Functionalized nanoparticles and method

ABSTRACT

A nanoparticle including an inorganic core comprising at least one metal and/or at least one semi-conductor compound comprising at least one metal includes a coating or shell disposed over at least a portion of a surface of the core. The coating can include one or more layers. Each layer of the coating can comprise a metal and/or at least one semiconductor compound. The nanoparticle further includes a ligand attached to a surface of the coating. The ligand is represented by the formula: X-Sp-Z, wherein X represents, e.g., a primary amine group, a secondary amine group, a urea, a thiourea, an imidizole group, an amide group, a phosphonic or arsonic acid group, a phosphinic or arsinic acid group, a phosphate or arsenate group, a phosphine or arsine oxide group; Sp represents a spacer group, such as a group capable of allowing a transfer of charge or an insulating group; and Z represents: (i) a reactive group capable of communicating specific chemical properties to the nanocrystal as well as provide specific chemical reactivity to the surface of the nanocrystal, and/or (ii) a group that is cyclic, halogenated, or polar a-protic. In certain embodiments, at least two chemically distinct ligands are attached to an surface of the coating, wherein the at least two ligands (I and II) are represented by the formula: X-Sp-Z. In ligand (I) X represents a phosphonic, phosphinic, or phosphategroup and in ligand (II) X represents a primary or secondary amine, or an imidizole, or an amide; In both ligands (I) and (II) Sp, which can be the same or different in the two compounds, represents a spacer group, such as a group capable of allowing a transfer of charge or an insulating group; Z, which can be the same or different in the two compounds, is a group chosen from among groups capable of communicating specific chemical properties to the nanoparticle as well as provide specific chemical reactivity to the surface of the nanoparticle. In preferred embodiments, the nanoparticle includes a core comprising a semiconductor material.

This application is a continuation of U.S. patent application Ser. No.12/722,028 filed 11 Mar. 2010, which is a continuation of commonly ownedInternational Application No. PCT/US2008/010651 filed 12 Sep. 2008,which was published in the English language as PCT Publication No. WO2009/035657 on 19 Mar. 2009, which International application claimspriority to U.S. Application Nos. 60/971,887, filed 12 Sep. 2007;60/992,598, filed 5 Dec. 2007; and 61/083,998, filed 28 Jul. 2008; eachof the foregoing hereby being incorporated herein by reference in itsentirety.

International Application No. PCT/US2008/010651 further claims priorityto U.S. Application Nos. 60/971,885, filed 12 Sep. 2007; 60/973,644,filed 19 Sep. 2007; and 61/016,227, filed 21 Dec. 2007. InternationalApplication No. PCT/US2008/010651 is also a continuation-in-partapplication of commonly owned International Application No.PCT/US2007/024750, filed 3 Dec. 2007. International Application No.PCT/US2008/010651 is also a continuation-in-part application of commonlyowned International Application No. PCT/US2008/007902, filed 25 Jun.2008. International Application No. PCT/US2008/010651 is also acontinuation-in-part application of commonly owned InternationalApplication No. PCT/US2007/013152, filed 4 Jun. 2007, which waspublished in the English language as PCT Publication No. WO 2007/143197on 13 Dec. 2007. PCT Application No. PCT/US2007/013152 claims priorityfrom commonly owned U.S. patent application Nos. 60/810,767 filed 2 Jun.2006, 60/810,914 filed 5 Jun. 2006, 60/804,921 filed 15 Jun. 2006,60/825,373 filed 12 Sep. 2006, 60/825,374 filed 12 Sep. 2006, 60/825,370filed 12 Sep. 2006, and 60/886,261 filed 23 Jan. 2007.

TECHNICAL FIELD

The present invention relates to the technical field of nanoparticlesand more particularly nanoparticles including ligands and relatedmethods.

BACKGROUND

A predominant method for the synthesis of colloidal quantum dotsinvolves reactions done in high boiling solvents, such astrioctylphosphine oxide (TOPO), trioctylphosphine (TOP), aliphaticphosphonic or carboxylic acids, and aliphatic amine species. The ligandcapping groups on the surface of the quantum dots are, therefore,believed to be a statistical distribution of TOPO, TOP, acid, and amine.Throughout the quantum dot literature, in order to affect surfacechemistry changes on a particular quantum dot sample (e.g. makingwater-soluble quantum dots), typical procedures involve cap exchangereactions, whereby already synthesized quantum dots (core or core-shell)are placed in a solution of another ligand and heated for an extendedperiod of time in order to drive off the existing ligands and replacethem with the alternate species. These procedures can be detrimental tomaintaining the optical properties of the quantum dots and often resultin drastically reduced emission efficiencies and stability.

Alternative techniques utilize self-assembled micelles that surround andinter-digitate with the native quantum dot surface ligands. The drawbackof these methods include the requirement for polar solvent environmentsto generate the encapsulating micelle, and thus limiting the techniqueto aqueous based applications, such as biological tagging and imaging.

Thus, there remains a need for a semiconductor nanocrystal includingfunctionalized ligands that are compatible with an organic based solventsystem, and methods for preparing same.

SUMMARY OF THE INVENTION

The present invention relates to nanoparticles including one or moreligands attached to a surface of the nanoparticle. The present inventionalso relates to methods for preparing a nanoparticle in the presence ofone or more ligands.

In accordance with one aspect of the present invention, there isprovided a nanoparticle including one or more chemically distinct nativeligands attached to a surface thereof, at least one of said ligandsbeing represented by the formula:X-Sp-Zwherein X represents a primary amine group, a secondary amine group, aurea, a thiourea, an imidizole group, an amide group, a phosphonic orarsonic acid group, a phosphinic or arsinic acid group, a phosphate orarsenate group, a phosphine or arsine oxide group; Sp represents aspacer group, such as a group capable of allowing a transfer of chargeor an insulating group; and Z represents: (i) a reactive group capableof communicating specific chemical properties to the nanoparticle aswell as provide specific chemical reactivity to the surface of thenanoparticle, and/or (ii) a group that is cyclic, halogenated, and/orpolar a-protic, wherein Z in all cases is not reactive upon exposure tolight.

As used herein, “native ligand” refers to a ligand that attaches orcoordinates to a nanoparticle surface during the growth or overcoatingthereof. Ligands are considered chemically distinct when they havedifferent chemical compositions.

In certain embodiments, Z does not render the nanoparticle dispersiblein a liquid medium that includes water.

In certain embodiments, a reactive group can comprise a functional,bifunctional, or polyfunctional reagent, and/or a reactive chemicalgroup.

As used herein, “reactive chemical group” refers to a chemical groupthat can react with one or more other groups or species. Examples ofreactive chemical groups include functional substituent groups. Examplesof functional substituent groups include, but are not limited to, thiol,carboxyl, hydroxyl, amino, amine, sulfo, bifunctional groups,polyfunctional groups, etc.)

In certain embodiments, a cyclic group can comprise a saturated orunsaturated cyclic (including, but not limited to, a single ring, abicyclic structure, a multi-cyclic structure, etc.) compound or aromaticcompound. In certain embodiments, the cyclic group can include at leastone hetero-atom. In certain embodiments, the cyclic group can include atleast one substituent group (including, for example, but not limited to,a reactive chemical group, an organic group (alky, aryl, etc.), etc.).Other examples of cyclic groups are provided herein.

In certain embodiments, a halogenated group can comprise a fluorinatedgroup, a perfluorinated group, a chlorinated group, a perchlorinatedgroup, a brominated group, a perbrominated group, an iodinated group, aperiodinated group, etc. Other examples of halogenated groups areprovided herein.

In certain embodiments, a polar a-protic group can comprise a ketone,aldehyde, amide, urea, urethane, or an imine. Other examples of polara-protic groups are provided herein.

In certain embodiments, a nanoparticle can comprise a semiconductormaterial.

In certain embodiments, a nanoparticle can comprise a core comprising afirst material and a shell (or coating material) disposed over at leasta portion of a surface of the core, the shell comprising a secondmaterial. In certain embodiments, the first material comprises asemiconductor material. In certain embodiments, the second materialcomprises a semiconductor material. In certain embodiments, one or moreadditional shells are disposed over at least a portion of a surface ofthe shell.

In certain preferred embodiments, a nanoparticle comprises asemiconductor nanocrystal. (A semiconductor nanocrystal is also referredto herein as a quantum dot.) In certain embodiments, the semiconductornanocrystal can comprise a core comprising a first material and a shell(or coating material) disposed over at least a portion of a surface ofthe core, the shell comprising a second material. Preferably, the secondmaterial comprises a nanocrystalline semiconductor material. In certainembodiments, one or more additional shells are disposed over at least aportion of a surface of the shell. Additional discussion ofnanoparticles and semiconductor nanocrystals is provided elsewhereherein.

Preferred ligands comprise benzylphosphonic acid, benzylphosphonic acidincluding at least one substituent group on the ring of the benzylgroup, a conjugate base of such acids, and mixtures including one ormore of the foregoing. In certain embodiments, a ligand comprises4-hydroxybenzylphosphonic acid, a conjugate base of the acid, or amixture of the foregoing. In certain embodiments, a ligand comprises3,5-di-tert-butyl-4-hydroxybenzylphosphonic acid, a conjugate base ofthe acid, or a mixture of the foregoing.

Other preferred ligands include ligands being represented by the formulaX-Sp-Z comprising an organic amine including a terminal hydroxyl groupor a fluorinated organic amine.

In certain preferred embodiments, a nanoparticle comprises asemiconductor nanocrystal core comprising a first semiconductor materialhaving an overcoating material comprising a second semiconductormaterial disposed on at least a portion of a surface of the core,wherein the overcoating material is grown thereon in the presence of oneor more of the ligands described herein.

In certain embodiments, a nanoparticle can include two or morechemically distinct native ligands attached to a surface thereof, atleast one of said ligands being represented by the formula:X-Sp-Z,wherein X, Sp, and Z are as described herein.

In certain embodiments, a nanoparticle can include two or morechemically distinct ligands attached to a surface thereof, a firstligand is represented by the formula:N-Sp-Z

wherein N represents a primary amine group, a secondary amine group, animidizole group, an amide group; and

a second ligand is represented by the formula:Y-Sp-Z

wherein Y represents a phosphonic or arsonic acid group, a phosphinic orarsinic acid group, a phosphate or arsenate group, a phosphine or arsineoxide group; and

wherein Sp, and Z are as described herein, and wherein each of Sp and Zon the first ligand and on the second ligand can be the same ordifferent.

In certain embodiments, Z does not render the nanoparticle dispersiblein a liquid medium that includes water.

The nanoparticle can be as described above and elsewhere herein.

Preferred ligands include benzylphosphonic acid, benzylphosphonic acidincluding at least one substituent group on the ring of the benzylgroup, a conjugate base of such acids, and mixtures including one ormore of the foregoing. In certain embodiments, a ligand comprises4-hydroxybenzylphosphonic acid, a conjugate base of the acid, and amixture of the foregoing. In certain embodiments, a ligand comprises3,5-di-tert-butyl-4-hydroxybenzylphosphonic acid, a conjugate base ofthe acid, or a mixture of the foregoing.

Other preferred ligands include ligands being represented by the formulaX-Sp-Z comprising an organic amine including a terminal hydroxyl groupor a fluorinated organic amine.

In accordance with another aspect of the present invention, there isprovided a method for functionalizing a nanoparticle. The methodcomprises reacting precursors for forming a nanoparticle having apredetermined composition in the presence of one or more chemicallydistinct ligands, at least one of the ligands being represented by theformula:X-Sp-Zwherein X represents a primary amine group, a secondary amine group, animidizole group, an amide group, a phosphonic or arsonic acid group, aphosphinic or arsinic acid group, a phosphate or arsenate group, aphosphine or arsine oxide group; Sp represents a spacer group, such as agroup capable of allowing a transfer of charge or an insulating group;and Z represents: (i) a reactive group capable of communicating specificchemical properties to the nanoparticle as well as provide specificchemical reactivity to the surface of the nanoparticle and/or (ii) agroup that is cyclic, halogenated, and/or polar a-protic, wherein Z inall cases is not reactive upon exposure to light.

In certain embodiments, Z does not render the nanoparticle dispersiblein a liquid medium that includes water.

In certain embodiments, a reactive group can comprise a functional,bifunctional, or polyfunctional reagent, and/or a reactive chemicalgroup.

In certain embodiments, a cyclic group can comprise a saturated orunsaturated cyclic (including, but not limited to, a single ring, abicyclic structure, a multi-cyclic structure, etc.) compound or aromaticcompound. In certain embodiments, the cyclic group can include at leastone hetero-atom. In certain embodiments, the cyclic group can include atleast one substituent group (including, for example, but not limited to,a reactive chemical group, an organic group (alky, aryl, etc.), etc.)Other examples of cyclic groups are provided herein.

In certain embodiments, a halogenated group can comprise a fluorinatedgroup, perfluorinated group, a chlorinated group, a perchlorinatedgroup, a brominated group, a perbrominated group, an iodinated group, aperiodinated group, etc. Other examples of halogenated groups areprovided herein.

In certain embodiments, a polar a-protic group can comprise a ketone,aldehyde, amide, urea, urethane, or an imine. Other examples of polara-protic groups are provided herein.

In certain embodiments, the predetermined composition of thenanoparticle comprises a semiconductor material.

In certain preferred embodiments, the predetermined compositioncomprises one or more metals and one or more chalcogens or pnictogens

In certain embodiments, precursors include one or more metal-containingprecursors and one or more chalcogen-containing or pnictogen-containingprecursors.

In certain embodiments, a nanoparticle can comprise a core comprising afirst material and a shell (or coating material) disposed over at leasta portion of a surface of the core, the shell comprising a secondmaterial. In certain embodiments, the first material comprises asemiconductor material. In certain embodiments, the second materialcomprises a semiconductor material. In certain embodiments, one or moreadditional shells are disposed over at least a portion of a surface ofthe shell.

In certain preferred embodiments, a nanoparticle comprises asemiconductor nanocrystal. In certain embodiments, the semiconductornanocrystal can comprise a core comprising a first material and a shell(or coating material) disposed over at least a portion of a surface ofthe core, the shell comprising a second material. Preferably, the secondmaterial comprises a nanocrystalline semiconductor material. In certainembodiments, one or more additional shells are disposed over at least aportion of a surface of the shell.

Preferred ligands include benzylphosphonic acid, benzylphosphonic acidincluding at least one substituent group on the ring of the benzylgroup, a conjugate base of such acids, and mixtures including one ormore of the foregoing. In certain embodiments, a ligand comprises4-hydroxybenzylphosphonic acid, a conjugate base of the acid, andmixtures including one or more of the foregoing. In certain embodiments,a ligand comprises 3,5-di-tert-butyl-4-hydroxybenzylphosphonic acid, aconjugate base of the acid, or a mixture of the foregoing.

Other preferred ligands include ligands being represented by the formulaX-Sp-Z comprising an organic amine including a terminal hydroxyl groupor a fluorinated organic amine.

In certain embodiments, the precursors are reacted in the presence oftwo or more chemically distinct ligands, at least one of said ligandsbeing represented by the formula:X-Sp-Z,wherein X, Sp, and Z are as described herein.

In certain embodiments, the precursors comprise one or moremetal-containing precursors and one or more chalcogen-containingprecursors or pnictogen-containing precursors.

In certain embodiments, the precursors are reacted in the presence oftwo or more chemically distinct ligands, wherein a first ligand isrepresented by the formula:N-Sp-Z

wherein N represents a primary amine group, a secondary amine group, animidizole group, an amide group; and

a second ligand is represented by the formula:Y-Sp-Z

wherein Y represents a phosphonic or arsonic acid group, a phosphinic orarsinic acid group, a phosphate or arsenate group, a phosphine or arsineoxide group; and

wherein Sp, and Z are as described herein, and wherein each of Sp and Zon the first ligand and on the second ligand can be the same ordifferent.

In certain embodiments, the precursors comprise one or moremetal-containing precursors and one or more chalcogen-containingprecursors or pnictogen-containing precursors.

In accordance with another aspect of the present invention, there isprovided a method for overcoating at least a portion of a surface of ananoparticle with a coating material having a predetermined composition,the method comprising reacting precursors for the predeterminedcomposition in the presence of one or more chemically distinct ligands,at least of the ligands being represented by the formula:X-Sp-Zwherein X represents a primary amine group, a secondary amine group, animidizole group, an amide group, a phosphonic or arsonic acid group, aphosphinic or arsinic acid group, a phosphate or arsenate group, aphosphine or arsine oxide group; Sp represents a spacer group, such as agroup capable of allowing a transfer of charge or an insulating group;and Z represents: (i) a reactive group capable of communicating specificchemical properties to the nanoparticle as well as provide specificchemical reactivity to the surface of the nanoparticle and/or (ii) agroup that is cyclic, halogenated, and/or polar a-protic, wherein Z inall cases is not reactive upon exposure to light.

In certain embodiments, Z does not render the nanoparticle dispersiblein a liquid medium that includes water.

In certain embodiments, a reactive group can comprise a functional,bifunctional, or polyfunctional reagent, and/or a reactive chemicalgroup.

In certain embodiments, a cyclic group can comprise a saturated orunsaturated cyclic (including, but not limited to, a single ring, abicyclic structure, a multi-cyclic structure, etc.) compound or aromaticcompound. In certain embodiments, the cyclic group can include at leastone hetero-atom.

In certain embodiments, the cyclic group can include at least onesubstituent group (including, for example, but not limited to, areactive chemical group, an organic group (alky, aryl, etc.), etc.).Other examples of cyclic groups are provided herein.

In certain embodiments, a halogenated group can comprise a fluorinatedgroup, perfluorinated group, a chlorinated group, a perchlorinatedgroup, a brominated group, a perbrominated group, an iodinated group, aperiodinated group, etc. Other examples of halogenated groups areprovided herein.

In certain embodiments, a polar a-protic group can comprise a ketone,aldehyde, amide, urea, urethane, or an imine. Other examples of polara-protic groups are provided herein.

In certain embodiments, the nanoparticle comprises a semiconductormaterial.

In certain embodiments, the nanoparticle can comprise a core comprisinga first material and a shell (or coating material) disposed over atleast a portion of a surface of the core, the shell comprising a secondmaterial. In certain embodiments, the first material comprises asemiconductor material. In certain embodiments, the second materialcomprises a semiconductor material. In certain embodiments, one or moreadditional shells are disposed over at least a portion of a surface ofthe shell.

In certain preferred embodiments, a nanoparticle comprises asemiconductor nanocrystal. In certain embodiments, the semiconductornanocrystal can comprise a core comprising a first material and a shell(or coating material) disposed over at least a portion of a surface ofthe core, the shell comprising a second material. Preferably, the secondmaterial comprises a nanocrystalline semiconductor material. In certainembodiments, one or more additional shells are disposed over at least aportion of a surface of the shell.

In certain embodiments, the predetermined composition of the coatingmaterial comprises a semiconductor material, preferably ananocrystalline semiconductor material.

In certain preferred embodiments, the predetermined compositioncomprises one or more metals and one or more chalcogens or pnictogens

In certain embodiments, precursors include one or more metal-containingprecursors and one or more chalcogen-containing or pnictogen-containingprecursors.

Preferred ligands include benzylphosphonic acid, benzylphosphonic acidincluding at least one substituent group on the ring of the benzylgroup, a conjugate base of such acids, and mixtures including one ormore of the foregoing. In certain embodiments, a ligand comprises4-hydroxybenzylphosphonic acid, a conjugate base of the acid, and amixture of the foregoing. In certain embodiments, a ligand comprises3,5-di-tert-butyl-4-hydroxybenzylphosphonic acid, a conjugate base ofthe acid, or a mixture of the foregoing.

Other preferred ligands include ligands being represented by the formulaX-Sp-Z comprising an organic amine including a terminal hydroxyl groupor a fluorinated organic amine.

In certain embodiments, the precursors are reacted in the presence oftwo or more chemically distinct ligands, at least one of said ligandsbeing represented by the formula:X-Sp-Z,wherein X, Sp, and Z are as described herein.

In certain embodiments, the precursors are reacted in the present of twoor more chemically distinct ligands, wherein a first ligand isrepresented by the formula:N-Sp-Z

wherein N represents a primary amine group, a secondary amine group, animidizole group, an amide group; and

a second ligand is represented by the formula:Y-Sp-Z

wherein Y represents a phosphonic or arsonic acid group, a phosphinic orarsinic acid group, a phosphate or arsenate group, a phosphine or arsineoxide group; and

wherein Sp, and Z are as described herein, and wherein each of Sp and Zon the first ligand and on the second ligand can be the same ordifferent.

In another aspect of the present invention, there is provided a methodfor preparing nanocrystals comprising a semiconductor material, themethod comprising heating a mixture comprising a liquid medium andsemiconductor material precursors in the presence of a first ligandcompound including an amine group (e.g., N-Sp-Z, wherein N represents aprimary amine group, a secondary amine group, an imidizole group, anamide group) and a second ligand compound including an acid group (e.g.,Y-Sp-Z, wherein Y represents a phosphonic or arsonic acid group, aphosphinic or arsinic acid group, a phosphate or arsenate group, aphosphine or arsine oxide group). Sp and Z are as described herein.

In certain preferred embodiments the first ligand compound including anamine group and second ligand compound including an acid group areinitially present in an equimolar amount, the equimolar amount beingdetermined based on the amine group content of the first ligand compoundand the acid group content of the second ligand compound.

In certain embodiments, the first ligand compound is represented by theformula A-L, wherein A is the acid group and L comprises an aryl group,a heteroaryl group, or a straight or branched C₁₋₁₈ hydrocarbon chain.In certain embodiments, the second ligand compound is represented by theformula N-L, wherein N is the amine group and L comprises an aryl group,a heteroaryl group, or a straight or branched C₁₋₁₈ hydrocarbon chain.In certain embodiments, the hydrocarbon chain includes at least onedouble bond, at least one triple bond, or at least one double bond andone triple bond. In certain embodiments, the hydrocarbon chain isinterrupted by —O—, —S—, —N(R_(a))—, —N(R_(a))—C(O)—O—,—O—C(O)—N(R_(a))—, —N(R_(a))—C(O)—N(R_(b))—, —O—C(O)—O—, —P(R_(a))—, or—P(O)(R_(a))—, wherein each of R_(a) and R_(b) independently, ishydrogen, alkyl, alkenyl, alkynyl, alkoxy, hydroxylalkyl, hydroxyl, orhaloalkyl. In certain embodiments, the aryl group is a substituted orunsubstituted cyclic aromatic group. In certain embodiments, the arylgroup includes phenyl, benzyl, naphthyl, tolyl, anthracyl, nitrophenyl,or halophenyl. In certain embodiments, the heteroaryl group comprises anaryl group with one or more heteroatoms in the ring, for instance furyl,pyridyl, pyrrolyl, phenanthryl. In certain embodiments, A comprises aphosphinic acid group or a carboxylic acid group. In certainembodiments, A comprises an oleic acid group or a myristic acid group.In certain preferred embodiments, A comprises a phosphonic acid group.

In certain embodiments of the methods described herein, the method iscarried out in a liquid medium. Preferably, the liquid medium comprisesa coordinating solvent or mixture of coordinating solvents. Examples ofcoordinating solvents including those provided herein. Othercoordinating solvents can also be used. In certain embodiments, themethod can be carried out in a liquid medium comprising anon-coordinating solvent or mixture of non-coordinating solvents.Examples of non-coordinating solvents include, but are not limited to,squalane, octadecane, or any other saturated hydrocarbon molecule.Mixtures of two or more solvents can also be used. Other suitablenon-coordinating solvents can be readily ascertained by one of ordinaryskill in the art.

In certain aspects and embodiments of the inventions described orcontemplated by this general description, the following detaileddescription, and claims, a nanoparticle can include a core and anovercoating (also referred to herein as a shell). A nanoparticleincluding a core and shell is also referred to as having a core/shellstructure. The shell is disposed over at least a portion of the core. Incertain embodiments, the shell is disposed over all or substantially allof the outer surface of the core. In certain embodiments of ananoparticle including a core/shell structure, the core can comprise afirst semiconductor material and the shell can comprise a secondsemiconductor material. In certain embodiments, the core comprises asemiconductor nanocrystal. In certain embodiments, a nanocrystal canhave a diameter of less than about 10 nanometers. In embodimentsincluding a plurality of nanoparticles, the distribution ofnanoparticles sizes is preferably monodisperse.

In certain aspects and embodiments of the inventions described orcontemplated by this general description, the following detaileddescription, and claims, a nanoparticle is water insoluble or notdispersible in a liquid medium comprising water.

In certain aspects and embodiments of the inventions described orcontemplated by this general description, the following detaileddescription, and claims, a nanoparticle comprising a semiconductormaterial (preferably, a semiconductor nanocrystal) is at least partiallyovercoated with a coating in the presence of one or more of the ligandstaught herein. In certain embodiments, the coating comprises more thanone material. In certain embodiments including a coating comprising morethan one material, the materials are applied sequentially. In certainembodiments, a core can include multiple overcoats or shells disposed ona surface thereof. Each of the multiple overcoats or shells can comprisethe same or different composition. In certain aspects and embodiments ofthe inventions described or contemplated by this general description,the following detailed description, and claims, a method is carried outin a non-aqueous medium. In certain preferred embodiments, the method isa colloidal synthesis method.

The foregoing, and other aspects and embodiments described herein allconstitute embodiments of the present invention.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory onlyand are not restrictive of the invention as claimed. Other embodimentswill be apparent to those skilled in the art from consideration of thespecification and practice of the invention disclosed herein.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 represents the chemical structures of examples of certaincompositions useful in carrying out the present invention.

FIG. 2 depicts Atomic Force Microscope images showing 5 nm CBP thermallyevaporated on an aliphatic ligand quantum dot monolayer.

FIG. 3 depicts Atomic Force Microscope images showing 15 nm CBPthermally evaporated on an aliphatic ligand quantum dot monolayer.

FIG. 4 depicts Atomic Force Microscope images showing 5 nm CBP thermallyevaporated on an aromatic ligand quantum dot monolayer.

FIG. 5 depicts Atomic Force Microscope images showing the effect ofligand composition on semiconductor nanocrystal layer interfacemorphology.

FIG. 6 represents the chemical structures of examples of certaincompositions useful in carrying out the present invention.

FIG. 7 represents the chemical structures of examples of certaincompositions useful in carrying out the present invention.

FIG. 8 depicts spectra to illustrate a method for measuring quantumefficiency.

The attached figures are simplified representations presented forpurposes of illustration only; the actual structures may differ innumerous respects, including, e.g., relative scale, etc.

For a better understanding to the present, invention, together withother advantages and capabilities thereof, reference is made to thefollowing disclosure and appended claims in connection with theabove-described drawings.

DETAILED DESCRIPTION OF THE INVENTION

In accordance with certain embodiments of the present invention there isprovided a nanoparticle including a ligand attached to a surfacethereof, the ligand being represented by the formula:X-Sp-Z

wherein:

X represents a primary amine group, a secondary amine group, a urea, athiourea, an imidizole group, an amide group, a phosphonic or arsonicacid group, a phosphinic or arsinic acid group, a phosphate or arsenategroup, a phosphine or arsine oxide group;

Sp represents a spacer group, such as a group capable of allowing atransfer of charge or an insulating group; and

Z represents: (i) a reactive group capable of communicating specificchemical properties to the nanocrystal as well as provide specificchemical reactivity to the surface of the nanocrystal, and/or (ii) agroup that is cyclic, halogenated, or polar a-protic. The ligandattaches or coordinates to a surface of the nanoparticle duringformation or overcoating thereof.

Examples of Sp include, but are not limited to, straight or branchedC₁-C₁₈ hydrocarbon chains. In certain embodiments, the hydrocarbon chainincludes at least one double bond, at least one triple bond, or at leastone double bond and one triple bond. In certain embodiments, thehydrocarbon chain is interrupted by —O—, —S—, —N(R_(a))—,—N(R_(a))—C(O)—O—, —O—C(O)—N(R_(a))—, —N(R_(a))—C(O)—N(R_(b))—,—O—C(O)—O—, —P(Ra)—, or —P(O)(R_(a))—, wherein each of R_(a) and R_(b),independently, is hydrogen, alkyl, alkenyl, alkynyl, alkoxy,hydroxylalkyl, hydroxyl, or haloalkyl.

Examples of reactive groups include, without limitation, functional,bifunctional, and polyfunctional reagents (e.g., homobifunctional orheterobifunctional), and reactive chemical groups (e.g., thiol, orcarboxyl, hydroxyl, amino, amine, sulfo, and the like). Examples ofadditional reactive groups include carbodithioate, carbodithioic acid,thiourea, amide, phosphine oxide, phosphonic or phosphinic acid,thiophosphonic or thiophosphinic acid, which can be substituted withalkyl and/or aryl units that are perhalogenated or partiallyhalogenated. Examples of cyclic groups include, but are not limited to,saturated or unsaturated cyclic or bicyclic compounds (e.g. cyclohexyl,isobornyl, etc.), or aromatic compounds (e.g. phenyl, benyl, naphthyl,biphenyl, fluorenyl, triarylamine, etc.). In certain embodiments, acyclic group can include one or more substituent groups (including, forexample, but not limited to, a reactive chemical group, an organic group(alky, aryl, etc.), etc.). Halogenated groups include, but are notlimited to, fluorinated groups, perfluorinated groups, (e.g.perfluoroalkyl, perfluorophenyl, perfluoroamines, etc.), chlorinatedgroups, perchlorinated groups. Examples of polar a-protic groupsinclude, but are not limited to, ketones, aldehydes, amides, ureas,urethanes, imines, etc.

In certain embodiments, the group comprising Z imparts predeterminedchemical miscibility properties to the semiconductor nanocrystal towhich it is attached.

In certain embodiments, Z does not include a non-functionalized straightor branched C₁-C₁₈ hydrocarbon chain.

In certain embodiments, the nanoparticle comprises a semiconductornanoparticle. In certain preferred embodiments, the nanoparticlecomprises a semiconductor nanocrystal.

In accordance with certain embodiments, there is provided a nanoparticleincluding two or more chemically distinct ligands attached to a surfacethereof, at least one of said ligands being represented by the formula:X-Sp-Z

wherein:

X represents a primary amine group, a secondary amine group, a urea, athiourea, an imidizole group, an amide group, phosphonic or arsonic acidgroup, a phosphinic or arsinic acid group, a phosphate or arsenategroup, a phosphine or arsine oxide group;

Sp represents a spacer group, such as a group capable of allowing atransfer of charge or an insulating group; and

Z represents: (i) a reactive group capable of communicating specificchemical properties to the nanocrystal as well as provide specificchemical reactivity to the surface of the nanocrystal, and/or (ii) agroup that is cyclic, halogenated, or polar a-protic.

Examples of Sp and Z include, without limitation, those describedherein.

In certain embodiments, Z does not include a non-functionalized straightor branched C₁-C₁₈ hydrocarbon chain.

In certain embodiments, the nanoparticle comprises a semiconductornanoparticle. In certain preferred embodiments, the nanoparticlecomprises a semiconductor nanocrystal.

In accordance with certain embodiments there is provided a nanoparticleincluding two or more chemically distinct ligands attached to a surfacethereof, wherein a first ligand is represented by the formula:N-Sp-Zwherein:

N represents a primary amine group, a secondary amine group, a urea, athiourea, an imidizole group, an amide group, or other nitrogencontaining functional group;

Sp represents a spacer group, such as a group capable of allowing atransfer of charge or an insulating group; and

Z represents a reactive group capable of communicating specific chemicalproperties to the nanocrystal and/or provide specific chemicalreactivity to the surface of the nanocrystal; and

a second ligand is represented by the formula:Y-Sp-Zwherein:

Y represents a phosphonic or arsonic acid group, a phosphinic or arsinicacid group, a phosphate or arsenate group, a phosphine or arsine oxidegroup, or other phosphorous-containing or arsenic-containing functionalgroup;

Sp represents a spacer group, such as a group capable of allowing atransfer of charge or an insulating group; and

Z represents a reactive group capable of communicating specific chemicalproperties to the nanocrystal and/or provide specific chemicalreactivity to the surface of the nanocrystal.

Examples of Sp and Z for inclusion in N-Sp-Z and P-Sp-Z include, withoutlimitation, those described herein. Sp and Z can be independentlyselected. Sp and Z included in each of the two ligands can be the sameor different.

In certain embodiments, Z does not include a non-functionalized straightor branched C₁-C₁₈ hydrocarbon chain.

In certain embodiments, the nanoparticle comprises a semiconductornanoparticle. In certain preferred embodiments, the nanoparticlecomprises a semiconductor nanocrystal.

In accordance with another embodiment of the invention, there isprovided a method for functionalizing a nanoparticle. The methodcomprises reacting precursors for forming a nanoparticle having apredetermined composition in the presence of the herein described ligandX-Sp-Z, wherein X, Sp, and Z are as described herein.

In certain embodiments, the nanoparticle comprises a semiconductornanoparticle. In certain preferred embodiments, the nanoparticlecomprises a semiconductor nanocrystal. In certain embodiments, thepredetermined precursors include a metal-containing precursor and achalcogen-containing or pnictogen-containing precursor. The precursorsare preferably included in the reaction mixture in amounts based on thepredetermined composition.

In certain embodiments, the method is carried out in a liquid medium.Preferably, the liquid medium comprises a coordinating solvent ormixture of coordinating solvents. Examples of coordinating solventsincluding those provided herein. Other coordinating solvents can also beused. In certain embodiments, the method can be carried out in a liquidmedium comprising a non-coordinating solvent or mixture ofnon-coordinating solvents. Examples of non-coordinating solventsinclude, but are not limited to, squalane, octadecane, or any othersaturated hydrocarbon molecule. Mixtures of two or more solvents canalso be used. Other suitable non-coordinating solvents can be readilyascertained by one of ordinary skill in the art.

In certain embodiments, the mole ratio of total metal included in theone or more metal-containing precursors to total moles of ligandrepresented by the formula X-Sp-Z is in the range from about 1:0.1 toabout 1:100. In certain embodiments, the mole ratio of total moles ofmetal included in the one or more metal-containing precursors to totalmoles of ligand represented by the formula X-Sp-Z is in the range fromabout 1:1 to about 1:50. In certain embodiments, the mole ratio of totalmoles of metal included in the one or more metal-containing precursorsto total moles of ligand represented by the formula X-Sp-Z is in therange from about 1:1 to about 1:30.

In certain embodiments in which the method is carried out in a liquidmedium, the mole ratio of total moles of the liquid medium to totalmoles of ligand represented by the formula X-Sp-Z is in the range fromabout 500:1 to about 2:1. In certain embodiments, the mole ratio oftotal moles of the liquid medium to total moles of ligand represented bythe formula X-Sp-Z is in the range from about 100:1 to about 5:1. Incertain embodiments, the mole ratio of total moles of the liquid mediumto total moles of ligand represented by the formula X-Sp-Z is in therange from about 50:1 to about 5:1.

In accordance with certain embodiments, there is provided a method forfunctionalizing a nanoparticle. The method comprises reacting precursorsfor forming a nanoparticle having a predetermined composition in thepresence of two or more chemically distinct ligands, at least one ofsaid ligands being represented by the formula:X-Sp-Z

wherein:

X represents a primary amine group, a secondary amine group, a urea, athiourea, an imidizole group, an amide group, phosphonic or arsonic acidgroup, a phosphinic or arsinic acid group, a phosphate or arsenategroup, a phosphine or arsine oxide group;

Sp represents a spacer group, such as a group capable of allowing atransfer of charge or an insulating group; and

Z represents: (i) a reactive group capable of communicating specificchemical properties to the nanocrystal as well as provide specificchemical reactivity to the surface of the nanocrystal, and/or (ii) agroup that is cyclic, halogenated, or polar a-protic.

In certain embodiments, Z does not include a non-functionalized straightor branched C₁-C₁₈ hydrocarbon chain. Examples of Sp and Z include,without limitation, those described herein.

In certain embodiments, the nanoparticle comprises a semiconductornanoparticle. In certain preferred embodiments, the nanoparticlecomprises a semiconductor nanocrystal. In certain embodiments, thepredetermined precursors include a metal-containing precursor and achalcogen-containing or pnictogen-containing precursor. The precursorsare preferably included in the reaction mixture in amounts based on thepredetermined composition.

In certain embodiments there is provided a method for functionalizing ananoparticle. The method comprises reacting precursors for forming ananoparticle having a predetermined composition in the presence of twoor more chemically distinct ligands, wherein a first ligand isrepresented by the formula:N-Sp-Z

wherein:

N represents a primary amine group, a secondary amine group, a urea, athiourea, an imidizole group, an amide group;

Sp represents a spacer group, such as a group capable of allowing atransfer of charge or an insulating group; and

Z represents a reactive group capable of communicating specific chemicalproperties to the nanocrystal as well as provide specific chemicalreactivity to the surface of the nanocrystal; and

a second ligand is represented by the formula:Y-Sp-Z

wherein:

Y represents phosphonic or arsonic acid group, a phosphinic or arsinicacid group, a phosphate or arsenate group, a phosphine or arsine oxidegroup;

Sp represents a spacer group, such as a group capable of allowing atransfer of charge or an insulating group; and

Z represents a reactive group capable of communicating specific chemicalproperties to the nanocrystal as well as provide specific chemicalreactivity to the surface of the nanocrystal.

Examples of Sp and Z include, without limitation, those describedherein. Sp and Z can be independently selected. Sp and Z included ineach of the two ligands can be the same or different.

In certain embodiments, the nanoparticle comprises a semiconductornanoparticle. In certain preferred embodiments, the nanoparticlecomprises a semiconductor nanocrystal. In certain embodiments, thepredetermined precursors include a metal-containing precursor and achalcogen-containing or pnictogen-containing precursor. The precursorsare preferably included in the reaction mixture in amounts based on thepredetermined composition. In accordance another embodiment of theinvention, there is provided a method for overcoating at least a portionof a surface of a nanoparticle with a coating material having apredetermined composition, the method comprising reacting precursors forthe predetermined coating material in the presence of a ligandrepresented by the formula X-Sp-Z and the nanoparticle to be coated,wherein X, Sp, and Z are as described herein. In certain embodiments,the nanoparticle comprises a semiconductor nanoparticle. In certainpreferred embodiments, the nanoparticle comprises a semiconductornanocrystal. In certain embodiments, the coating composition comprises asemiconductor material. In certain embodiments, the precursors include ametal-containing precursor and a chalcogen-containing orpnictogen-containing precursor. The precursors are preferably includedin the reaction mixture in amounts based on the predeterminedcomposition.

In certain embodiments, the method is carried out in a liquid medium.Preferably, the liquid medium comprises a coordinating solvent ormixture of coordinating solvents. Examples of coordinating solventsincluding those provided herein. Other coordinating solvents can also beused. In certain embodiments, the method can be carried out in a liquidmedium comprising a non-coordinating solvent or mixture ofnon-coordinating solvents. Examples of non-coordinating solventsinclude, but are not limited to, squalane, octadecane, or any othersaturated hydrocarbon molecule. Mixtures of two or more solvents canalso be used. Other suitable non-coordinating solvents can be readilyascertained by one of ordinary skill in the art.

In certain embodiments, the mole ratio of total metal included in thenanoparticles being overcoated to total moles of ligand represented bythe formula X-Sp-Z is in the range from about 1:0.1 to about 1:100. Incertain embodiments, the mole ratio of total moles of metal included inthe nanoparticles being overcoated to total moles of ligand representedby the formula X-Sp-Z is in the range from about 1:1 to about 1:50. Incertain embodiments, the mole ratio of total moles of metal included inthe nanoparticles being overcoated to total moles of ligand representedby the formula X-Sp-Z is in the range from about 1:1 to about 1:30.

In certain embodiments of the method being carried out in a liquidmedium, the mole ratio of total moles of the liquid medium to totalmoles of ligand represented by the formula X-Sp-Z is in the range fromabout 500:1 to about 2:1. In certain embodiments, the mole ratio oftotal moles of the liquid medium to total moles of ligand represented bythe formula X-Sp-Z is in the range from about 100:1 to about 5:1. Incertain embodiments, the mole ratio of total moles of the liquid mediumto total moles of ligand represented by the formula X-Sp-Z is in therange from about 50:1 to about 5:1. In accordance with furtherembodiments of the invention, there is provided a method for overcoatingat least a portion of a surface of a nanoparticle with a coatingmaterial having a predetermined composition, the method comprisingreacting precursors for the predetermined coating material in thepresence of two or more chemically distinct ligands and the nanoparticleto be coated, at least one of said ligands being represented by theformula:X-Sp-Zand the nanoparticle to be coated, wherein:

X represents a primary amine group, a secondary amine group, a urea, athiourea, an imidizole group, an amide group, phosphonic or arsonic acidgroup, a phosphinic or arsinic acid group, a phosphate or arsenategroup, a phosphine or arsine oxide group;

Sp represents a spacer group, such as a group capable of allowing atransfer of charge or an insulating group; and

Z represents: (i) a reactive group capable of communicating specificchemical properties to the nanocrystal as well as provide specificchemical reactivity to the surface of the nanocrystal, and/or (ii) agroup that is cyclic, halogenated, or polar a-protic.

In certain embodiments, Z does not include a non-functionalized straightor branched C₁-C₁₈ hydrocarbon chain.

Examples of Sp and Z include, without limitation, those describedherein.

In certain embodiments, the nanoparticle comprises a semiconductornanoparticle. In certain preferred embodiments, the nanoparticlecomprises a semiconductor nanocrystal. In certain embodiments, thecoating composition comprises a semiconductor material. In certainembodiments, the precursors include a metal-containing precursor and achalcogen-containing or pnictogen-containing precursor. The precursorsare preferably included in the reaction mixture in amounts based on thepredetermined composition.

In certain embodiments, there is provided a method for overcoating atleast a portion of a surface of a nanoparticle with a coating materialhaving a predetermined composition, the method comprising reactingprecursors for the predetermined coating material in the presence of twoor more chemically distinct ligands and the nanoparticle to be coated,wherein a first ligand is represented by the formula:N-Sp-Z

wherein:

N represents a primary amine group, a secondary amine group, a urea, athiourea, an imidizole group, an amide group;

Sp represents a spacer group, such as a group capable of allowing atransfer of charge or an insulating group; and

Z represents a reactive group capable of communicating specific chemicalproperties to the nanocrystal as well as provide specific chemicalreactivity to the surface of the nanocrystal; and

a second ligand is represented by the formula:Y-Sp-Z

wherein Y represents a phosphonic or arsonic acid group, a phosphinic orarsinic acid group, a phosphate or arsenate group, a phosphine or arsineoxide group;

Sp represents a spacer group, such as a group capable of allowing atransfer of charge or an insulating group; and Z represents a reactivegroup capable of communicating specific chemical properties to thenanocrystal as well as provide specific chemical reactivity to thesurface of the nanocrystal.

Examples of Sp and Z include, without limitation, those describedherein. Sp and Z can be independently selected. Sp and Z including inthe two ligands can be the same or different.

In certain embodiments, the nanoparticle comprises a semiconductornanoparticle. In certain preferred embodiments, the nanoparticlecomprises a semiconductor nanocrystal.

In certain embodiments, the coating composition comprises asemiconductor material. In certain embodiments, the precursors include ametal-containing precursor and a chalcogen-containing orpnictogen-containing precursor. The precursors are preferably includedin the reaction mixture in amounts based on the predeterminedcomposition.

In carrying out the methods described herein, the precursors areselected and reacted in amounts and under reaction conditions, and for aperiod of time, to produce a nanoparticle having the predeterminedcomposition. Such variables can be routinely determined by a person ofordinary skill in the relevant art. In certain embodiments, the reactionis carried out in a controlled atmosphere (substantially free of watermoisture and air). In certain preferred embodiments, the reaction iscarried out in a water-free inert atmosphere.

In certain embodiments of the present invention, a nanoparticle (e.g., asemiconductor nanocrystal) is formed, or overcoated in order to generatea shell on at least a portion of an outer surface of a nanoparticle, inthe presence of at least one molecule having the following formula:

Wherein R₁ represents a hydroxyl group; R₂ represents a hydroxyl,hydrogen, an alkyl or alkylene group, an aryl or arylene group, —OR₁₁,—NHR₁₁, —NR₁₁R₁₁, —SR₁₁, wherein R₁₁ represents hydrogen, an alkylgroup, or an aryl group; R₃ and R₄, which can be the same or different,represent a bond, an alkyl or alkylene group, an aryl or arylene group,a fluorocarbon group,

wherein R₁₂ is an alkyl or alkylene group or an aryl or arylene group;R₅ represents hydrogen, an alkyl group including one or more functionalgroups, an alkylene group, an aryl or arylene group, —OR₁₃, —NHR₁₃,—NR₁₃R₁₃, —SR₁₃, wherein R₁₃ represents hydrogen, an alkyl group, or anaryl group; R₆ represents hydrogen; R₇ represents hydrogen, an alkyl oralkylene group, an aryl or arylene group, —OR₁₄, —NHR₁₄, —NR₁₄R₁₄,—SR₁₄, wherein R₁₄ represents hydrogen, an alkyl group, or an arylgroup; Re and R₉, which can be the same or different, represent a bond,an alkylene group, an aryl or arylene group, a fluorocarbon group,

wherein R₁₅ is an alkyl or alkylene group or an aryl or arylene group;R₈ can also represent an alkyl group; R₉ can represent an alkyl groupincluding one or more functional groups; R₁₀ represents hydrogen, analkyl or alkylene group, an aryl or arylene group, —OR₁₆, —NHR₁₆,—NR₁₆R₁₆, —SR₁₆, wherein R₁₆ represents hydrogen, an alkyl group, or anaryl group.

Furthermore, the architecture described herein opens up the possibilityfor a modular synthetic scheme for tailoring a quantum dot surface withany desired characteristic. For example, a terminal hydroxyl groupprovides a site for additional chemical reactivity. The nucleophilicnature of the —OH group can do various addition and substitutionreactions with the appropriate electrophile. For example, quantum dots(e.g., semiconductor nanocrystals) with this nucleophilic surface groupcan be reacted with an electrophile, such as an acid chloride,isocyanate, or carboxylic acid group resulting in the following esterand urethane linkages:

Where R can be any substituent. The —OH group can also be substitutedfor a primary amine resulting in the following amide and urea linkageswith the electrophiles mentioned herein:

Where, again, R can be any substituent.

Functionalizing Surface of the Semiconductor Nanocrystal with TerminalHydroxyl Groups.

Chemical Structures Used:

This approach may be achieved in the presence of phosphine oxide (TOPO)with the addition of high boiling polar a-protic solvents (e.g.1,3-Dimethyl-2-imidazolidone (DMI), Carbitol Acetate,N,N-Dimethylacrylamide (DMAc), 1-Methyl-2-pyrrolidnone (NMP), etc.).

Examples of Coupling Species to Hydroxy-Terminated SemiconductorNanocrystals

The functional groups are isocyanates, acid chlorides, and carboxylicacids from left to right. Where R can be, and is most certainly notlimited to, any of the following chemical species (with any lengthaliphatic chain linker connecting the molecule to the functional groupshown herein).

The system described herein can be further augmented by building similarvariability into the phosphine oxide derivative used as the solvent inthe overcoating procedure. This species has the formula:

Wherein R₁₇, R₁₈, and R₁₉, which can be the same or different, representa bond, an alkyl or alkylene group, an aryl or arylene group, afluorocarbon group,

wherein R₂₃ is an alkyl or alkylene group or an aryl or arylene group;R₂₀, R₂₁, and R₂₂, which can be the same or different, representhydrogen, an alkyl or alkylene group, an aryl or arylene group, —OR₂₄,—NHR₂₄, —NR₂₄R₂₄, —SR₂₄, wherein R₂₄ represents hydrogen, an alkylgroup, or an aryl group.

To avoid the introduction of impurities which may have an unpredictableeffect on the reaction, the ligands should preferably have a purity ofat least 99 wt. %, and preferably greater than 99.5%.

Phosphinic or arsinic acid groups useful in the practice of theinvention may include mono- and di-phosphinic/arsinic acid groups.

In accordance with certain embodiments of the present invention, ananoparticle (e.g., a semiconductor nanocrystal) is formed, orovercoated in order to generate a shell on at least a portion of anouter surface of a nanoparticle, in the presence of moleculesrepresented by one of the following formula or in the presence ofmolecules of both of the following formula:

(in the above formula on the left, P can alternatively be As)

wherein R₁ represents a hydroxyl group; R₂ represents hydrogen, an alkylor alkylene group, an aryl or arylene group, —OR₁₁, —NHR₁₁, —NR₁₁R₁₁,—SR₁₁, wherein R₁₁ represents hydrogen, an alkyl group, or an arylgroup; R₃ and R₄, which can be the same or different, represent a bond,an alkyl or alkylene group, an aryl or arylene group, a fluorocarbongroup,

wherein R₁₂ is an alkyl or alkylene group or an aryl or arylene group;R₅ represents hydrogen, an alkyl group including one or more functionalgroups, an alkylene group, an aryl or arylene group, —OR₁₃, —NHR₁₃,—NR₁₃R₁₃, —SR₁₃, wherein R₁₃ represents hydrogen, an alkyl group, or anaryl group; R₆ represents hydrogen; R₇ represents hydrogen, an alkyl oralkylene group, an aryl or arylene group, —OR₁₄, —NHR₁₄, —NR₁₄R₁₄,—SR₁₄, wherein R₁₄ represents hydrogen, an alkyl group, or an arylgroup; R₈ and R₉, which can be the same or different, represent a bond,an alkyl or alkylene group, an aryl or arylene group, a fluorocarbongroup,

wherein R₁₅ is an alkyl or alkylene group or an aryl or arylene group;R₁₀ represents hydrogen, an alkyl group including one or more functionalgroups, an alkylene group, an aryl or arylene group, —OR₁₆, —NHR₁₆,—NR₁₆R₁₆, —SR₁₆, wherein R₁₆ represents hydrogen, an alkyl group, or anaryl group.

As mentioned herein, the system can be further augmented by buildingsimilar variability into the phosphine oxide derivative used as thesolvent in the overcoating procedure. This species has the formula:

Wherein R₁₇, R₁₈, and R₁₉, which can be the same or different, representa bond, an alkyl or alkylene group, an aryl or arylene group, afluorocarbon group,

wherein R₂₃ is an alkyl or alkylene group or an aryl or arylene group;R₂₀, R₂₁, and R₂₂, which can be the same or different, representhydrogen, an alkyl or alkylene group, an aryl or arylene group, —OR₂₄,—NHR₂₄, —NR₂₄R₂₄, —SR₂₄, wherein R₂₄ represents hydrogen, an alkylgroup, or an aryl group.

To avoid the introduction of impurities which may have an unpredictableeffect on the reaction, the ligands should preferably have a purity ofat least 99 wt. %, and preferably greater than 99.5%.

Phosphinic acid groups useful in the practice of the invention mayinclude mono and diphosphinic acid groups.

As described herein, arsenic variations of the above-describedphosphorus-containing acid and oxide groups can also be used.

The present invention will be further clarified by the followingexamples, which are intended to be exemplary of the present invention.

EXAMPLES Example 1A

Performing the overcoating procedure with TOPO as the solvent, replacingthe existing aliphatic phosphonic acid and amine species with aromaticderivatives (see FIG. 1) results in semiconductor nanocrystals that havenew surface chemistry while maintaining their optical properties. Thesesemiconductor nanocrystals are no longer soluble in hexane, but arereadily soluble in toluene and chloroform. In addition, thin films oforganic molecules can be reliably deposited onto ordered films of thesesynthetically modified nanocrystals without the “puddling” associatedwith traditional aliphatic semiconductor nanocrystal surface chemistry(see FIGS. 2-5). It is believed that a phosphonic acid/amine salt is thepredominant species on the surface of the semiconductor nanocrystaldespite the fact that TOPO is in large excess during the reaction.

Preparation of Aromatic Semiconductor Nanocrystals Capable of EmittingRed Light

Synthesis of CdSe Cores:

1 mmol cadmium acetate was dissolved in 8.96 mmol oftri-n-octylphosphine at 100° C. in a 20 mL vial and then dried anddegassed for one hour. 15.5 mmol of trioctylphosphine oxide and 2 mmolof octadecylphosphonic acid were added to a 3-neck flask and dried anddegassed at 140° C. for one hour. After degassing, the Cd solution wasadded to the oxide/acid flask and the mixture was heated to 270° C.under nitrogen. Once the temperature reached 270° C., 8 mmol oftri-n-butylphosphine was injected into the flask. The temperature wasbrought back to 270° C. where 1.1 mL of 1.5 M TBP-Se was then rapidlyinjected. The reaction mixture was heated at 270° C. for 15-30 minuteswhile aliquots of the solution were removed periodically in order tomonitor the growth of the nanocrystals. Once the first absorption peakof the nanocrystals reached 565-575 nm, the reaction was stopped bycooling the mixture to room temperature. The CdSe cores wereprecipitated out of the growth solution inside a nitrogen atmosphereglovebox by adding a 3:1 mixture of methanol and isopropanol. Theisolated cores were then dissolved in hexane and used to make core-shellmaterials.

Synthesis of CdSe/CdZnS Core-Shell Nanocrystals:

25.86 mmol of trioctylphosphine oxide and 2.4 mmol of benzylphosphonicacid were loaded into a four-neck flask. The mixture was then dried anddegassed in the reaction vessel by heating to 120° C. for about an hour.The flask was then cooled to 75° C. and the hexane solution containingisolated CdSe cores (0.1 mmol Cd content) was added to the reactionmixture. The hexane was removed under reduced pressure and then 2.4 mmolof phenylethylamine was added to the reaction mixture. Dimethyl cadmium,diethyl zinc, and hexamethyldisilathiane were used as the Cd, Zn, and Sprecursors, respectively. The Cd and Zn were mixed in equimolar ratioswhile the S was in two-fold excess relative to the Cd and Zn. The Cd/Znand S samples were each dissolved in 4 mL of trioctylphosphine inside anitrogen atmosphere glove box. Once the precursor solutions wereprepared, the reaction flask was heated to 155° C. under nitrogen. Theprecursor solutions were added dropwise over the course of 2 hours at155° C. using a syringe pump. After the shell growth, the nanocrystalswere transferred to a nitrogen atmosphere glovebox and precipitated outof the growth solution by adding a 3:1 mixture of methanol andisopropanol. The isolated core-shell nanocrystals were then dissolved intoluene. The semiconductor nanocrystals had an emission maximum of 616nm with a FWHM of 34 nm and a solution quantum yield of 50%.

Sample Fabrication.

Cleaned glass substrates were washed in a plasma preen and coated withPEDOT:PSS (70 nm). Substrates were taken into a nitrogen environment andbaked at 120 C for 20 minutes. 50 nm E105(N,N′-Bis(3-methylphenyl)-N,N′-bis-(phenyl)-9,9-spiro-bifluorene,LumTec) was evaporated in a vacuum chamber below 2e-6 Torr via thermalevaporation. Application of aromatic quantum dots was accomplished viacontact printing. A dispersion of semiconductor nanocrystals with anoptical density (OD) of 0.3 at the 1^(st) absorption feature wasspin-coated at 3000 rpm on a parylene coated stamp for 60 seconds, whichwas then stamped onto the E105 substrates depositing a mono-layer ofaromatic quantum dots. Substrates were then taken back into the thermalevaporation chamber, and 5 nm and 15 nm, respectively, of CBP(4,4′-Bis(carbazol-9-yl)biphenyl, LumTec) were evaporated below 2e-6Torr. FIGS. 2-5 depict images of the samples described in this SampleFabrication example.

Following examples 1-B and 1-C relate to preparing semiconductornanocrystals including benzyl phosphonic acid ligands, but without thephenylethylamine shown in FIG. 1:

Example 1-B Preparation of Semiconductor Nanocrystals Capable ofEmitting Green Light

Synthesis of ZnSe Cores:

0.69 mmol diethyl zinc was dissolved in 5 mL of tri-n-octylphosphine andmixed with 1 mL of 1 M TBP-Se. 28.9 mmol of Oleylamine was loaded into a3-neck flask, dried and degassed at 90° C. for one hour. Afterdegassing, the flask was heated to 310° C. under nitrogen. Once thetemperature reached 310° C., the Zn solution was injected and thereaction mixture was heated at 270° C. for 15-30 minutes while aliquotsof the solution were removed periodically in order to monitor the growthof the nanocrystals. Once the first absorption peak of the nanocrystalsreached 350 nm, the reaction was stopped by dropping the flasktemperature to 160° C. and used without further purification forpreparation of CdZnSe cores.

Synthesis of CdZnSe Cores:

1.12 mmol dimethylcadmium was dissolved in 5 mL of tri-n-octylphosphineand mixed with 1 mL of 1 M TBP-Se. In a 4-neck flask, 41.38 mmol oftrioctylphosphine oxide and 4 mmol of hexylphosphonic acid were loaded,dried and degassed at 120° C. for one hour. After degassing, theoxide/acid was heated to 160° C. under nitrogen and 8 ml of the ZnSecore growth solution was transferred at 160° C. into the flask,immediately followed by the addition of Cd/Se solution over the courseof 20 minutes via syringe pump. The reaction mixture was then heated at150° C. for 16-20 hours while aliquots of the solution were removedperiodically in order to monitor the growth of the nanocrystals. Oncethe emission peak of the nanocrystals reached 500 nm, the reaction wasstopped by cooling the mixture to room temperature. The CdZnSe coreswere precipitated out of the growth solution inside a nitrogenatmosphere glovebox by adding a 2:1 mixture of methanol and n-butanol.The isolated cores were then dissolved in hexane and used to makecore-shell materials.

Synthesis of CdZnSe/CdZnS Core-Shell Nanocrystals:

25.86 mmol of trioctylphosphine oxide and 2.4 mmol of benzylphosphonicacid were loaded into a four-neck flask. The mixture was then dried anddegassed in the reaction vessel by heating to 120° C. for about an hour.The flask was then cooled to 75° C. and the hexane solution containingisolated CdZnSe cores (0.1 mmol Cd content) was added to the reactionmixture. The hexane was removed under reduced pressure. Dimethylcadmium, diethyl zinc, and hexamethyldisilathiane were used as the Cd,Zn, and S precursors, respectively. The Cd and Zn were mixed inequimolar ratios while the S was in two-fold excess relative to the Cdand Zn. The Cd/Zn and S samples were each dissolved in 4 mL oftrioctylphosphine inside a nitrogen atmosphere glove box. Once theprecursor solutions were prepared, the reaction flask was heated to 150°C. under nitrogen. The precursor solutions were added dropwise over thecourse of 1 hour at 150° C. using a syringe pump. After the shellgrowth, the nanocrystals were transferred to a nitrogen atmosphereglovebox and precipitated out of the growth solution by adding a 3:1mixture of methanol and isopropanol. The isolated core-shellnanocrystals were then dissolved in hexane and used to makesemiconductor nanocrystal composite materials.

Example 1-C Preparation of Semiconductor Nanocrystals Capable ofEmitting Red Light

Synthesis of CdSe Cores:

1 mmol cadmium acetate was dissolved in 8.96 mmol oftri-n-octylphosphine at 100° C. in a 20 mL vial and then dried anddegassed for one hour. 15.5 mmol of trioctylphosphine oxide and 2 mmolof octadecylphosphonic acid were added to a 3-neck flask and dried anddegassed at 140° C. for one hour. After degassing, the Cd solution wasadded to the oxide/acid flask and the mixture was heated to 270° C.under nitrogen. Once the temperature reached 270° C., 8 mmol oftri-n-butylphosphine was injected into the flask. The temperature wasbrought back to 270° C. where 1.1 mL of 1.5 M TBP-Se was then rapidlyinjected. The reaction mixture was heated at 270° C. for 15-30 minuteswhile aliquots of the solution were removed periodically in order tomonitor the growth of the nanocrystals. Once the first absorption peakof the nanocrystals reached 565-575 nm, the reaction was stopped bycooling the mixture to room temperature. The CdSe cores wereprecipitated out of the growth solution inside a nitrogen atmosphereglovebox by adding a 3:1 mixture of methanol and isopropanol. Theisolated cores were then dissolved in hexane and used to make core-shellmaterials.

Synthesis of CdSe/CdZnS Core-Shell Nanocrystals:

25.86 mmol of trioctylphosphine oxide and 2.4 mmol of benzylphosphonicacid were loaded into a four-neck flask. The mixture was then dried anddegassed in the reaction vessel by heating to 120° C. for about an hour.The flask was then cooled to 75° C. and the hexane solution containingisolated CdSe cores (0.1 mmol Cd content) was added to the reactionmixture. The hexane was removed under reduced pressure. Dimethylcadmium, diethyl zinc, and hexamethyldisilathiane were used as the Cd,Zn, and S precursors, respectively. The Cd and Zn were mixed inequimolar ratios while the S was in two-fold excess relative to the Cdand Zn. The Cd/Zn and S samples were each dissolved in 4 mL oftrioctylphosphine inside a nitrogen atmosphere glove box. Once theprecursor solutions were prepared, the reaction flask was heated to 155°C. under nitrogen. The precursor solutions were added dropwise over thecourse of 2 hours at 155° C. using a syringe pump. After the shellgrowth, the nanocrystals were transferred to a nitrogen atmosphereglovebox and precipitated out of the growth solution by adding a 3:1mixture of methanol and isopropanol. The isolated core-shellnanocrystals were then dissolved in toluene and used to make quantum dotcomposite materials.

Example 2

Performing the overcoating procedure with TOPO as the solvent, afluorinated derivative of the amine species was used withhexylphosphonic acid, an aliphatic phosphonic acid (see FIG. 6). Afterthe reaction, these semiconductor nanocrystals were no longer soluble inconventional organic solvents, such as hexane, toluene, chloroform,methylene chloride, etc. However, the sample was soluble in fluorinatedsolvents such as perfluorohexane, perfluorotoluene, and Fluorinert(FC-77). The level of fluorination could be enhanced by using thefluorinated amine with a fluorinated phosphonic acid derivative and/or afluorinated TOPO equivalent in synthesis.

Fluorinating the surface of the semiconductor nanocrystals canfacilitate deposition of the material in various applications.Fluorinated semiconductor nanocrystals have been successfully spin-castdirectly onto organic thin-films since the fluorinated solvent wasunable to solvate the organic transport materials.

Example 3

Performing the overcoating procedure with TOPO as the solvent, an aminespecies functionalized with a terminal hydroxyl group was implementedwith hexylphosphonic acid (see FIG. 7). After the reaction, the samplewas not soluble in hexane or toluene but was soluble in polar solventssuch as methanol and isopropanol. Again, polarity of the semiconductornanocrystal surface could be enhanced by using an amine with an alkyl oraryl phosphonic acid with a terminal hydroxyl group and/or an alkyl oraryl phosphine oxide with a terminal hydroxyl group.

Example 4 Preparation of Semiconductor Nanocrystals Capable of EmittingRed Light

Synthesis of CdSe Cores:

1 mmol cadmium acetate was dissolved in 8.96 mmol oftri-n-octylphosphine at 100° C. in a 20 mL vial and then dried anddegassed for one hour. 15.5 mmol of trioctylphosphine oxide and 2 mmolof octadecylphosphonic acid were added to a 3-neck flask and dried anddegassed at 140° C. for one hour. After degassing, the Cd solution wasadded to the oxide/acid flask and the mixture was heated to 270° C.under nitrogen. Once the temperature reached 270° C., 8 mmol oftri-n-butylphosphine was injected into the flask. The temperature wasbrought back to 270° C. where 1.1 mL of 1.5 M TBP-Se was then rapidlyinjected. The reaction mixture was heated at 270° C. for 15-30 minuteswhile aliquots of the solution were removed periodically in order tomonitor the growth of the nanocrystals. Once the first absorption peakof the nanocrystals reached 565-575 nm, the reaction was stopped bycooling the mixture to room temperature. The CdSe cores wereprecipitated out of the growth solution inside a nitrogen atmosphereglovebox by adding a 3:1 mixture of methanol and isopropanol. Theisolated cores were then dissolved in hexane and used to make core-shellmaterials.

Synthesis of CdSe/CdZnS Core-Shell Nanocrystals:

25.86 mmol of trioctylphosphine oxide and 2.4 mmol ofoctadecylphosphonic acid were loaded into a four-neck flask. The mixturewas then dried and degassed in the reaction vessel by heating to 120° C.for about an hour. The flask was then cooled to 75° C. and the hexanesolution containing isolated CdSe cores (0.1 mmol Cd content) was addedto the reaction mixture. The hexane was removed under reduced pressureand then 2.4 mmol of 6-amino-1-hexanol was added to the reactionmixture. Dimethyl cadmium, diethyl zinc, and hexamethyldisilathiane wereused as the Cd, Zn, and S precursors, respectively. The Cd and Zn weremixed in equimolar ratios while the S was in two-fold excess relative tothe Cd and Zn. The Cd/Zn and S samples were each dissolved in 4 mL oftrioctylphosphine inside a nitrogen atmosphere glove box. Once theprecursor solutions were prepared, the reaction flask was heated to 155°C. under nitrogen. The precursor solutions were added dropwise over thecourse of 2 hours at 155° C. using a syringe pump. After the shellgrowth, the nanocrystals were transferred to a nitrogen atmosphereglovebox and precipitated out of the growth solution by adding a 3:1mixture of methanol and isopropanol. The isolated core-shellnanocrystals were then dissolved in hexane.

Preparation of Layer Including Semiconductor Nanocrystals

Films listed in Table 1 below are prepared using samples includingsemiconductor nanocrystals prepared substantially in accordance with oneof the above-described examples dispersed in hexane. (A sample typicallyrepresents approximately 40 mg of solid dispersed in 10-15 ml hexane.)The hexane is removed from the semiconductor nanocrystals under vacuumat room temperature. Care is taken not to overdry or completely removeall solvent. 0.5 ml of RD-12, a low viscosity reactive diluentcommercially available from Radcure Corp, 9 Audrey Pl, Fairfield, N.J.07004-3401, United States, is added to the semiconductor nanocrystalswhile stirring magnetically. After the semiconductor nanocrystals arepre-solubilized in the reactive diluent, 2 ml of DR-150, UV-curableacrylic formulation commercially available Radcure, is added dropwisewhile stirring vigorously. Occasionally, the mixing vial is heated tolower viscosity and aid stirring. After the addition is competed, vacuumis pulled to remove entrained air. The vial is then placed in anultrasonic bath (VWR) from 1 hour to overnight, resulting in a clear,colored solution. Care is taken to avoid temperatures over 40 C whilethe sample is in the ultrasonic bath.

Multiple batches of the semiconductor nanocrystals of the same color inUV curable acrylic are mixed together. For the samples below, the threered batches listed in Table 1 were added together; and four greenbatches listed in Table 1 were added together.

Samples are coated by Mayer rod on precleaned glass slides and cured ina 5000-EC UV Light Curing Flood Lamp from DYMAX Corporation system withan H-bulb (225 mW/cm²) for 10 seconds.

Samples including multiple layers for achieving the desired thicknessare cured between layers. Samples including filters on top of (or below)the semiconductor nanocrystal/matrix layers have the filters coated byMayer rod in a separate step. Filters are made by blending UV-curablepigment ink formulations from Coates/Sun Chemical. A filter compositionis formulated by adding the weighted absorbances of the individualcolors together to achieve the desired transmission characteristics.

TABLE 1 Film Solu- Color/Batch # Emis- tion (Nanocrystal Sol- sion QYPrep. Example #) vent Ligand(s) (nm) FWHM (%) Red/Batch #1 Hexane ODPAwith 6- 617 40 73 (Ex. 4) amino-1-hexanol Red/Batch # 2 Hexane ODPA with6- 622 44 82 (Ex. 4) amino-1-hexanol Red/Batch #3 Hexane ODPA with 6-624 44 73 (Ex. 4) amino-1-hexanol Green/Batch #1 Hexane Aromatic 525 3468 (Ex 1A) Green/Batch #2 Hexane Aromatic 527 34 66 (Ex 1A) Green/Batch#3 Hexane Aromatic 528 36 64 (Ex 1A) Green/Batch #4 Hexane Aromatic 53033 60 (Ex 1A) Green/Batch #5 Hexane Aromatic 529 33 68 (Ex 1A)

Examples of other variations for synthesizing semiconductor nanocrystalswith aromatic surface functionality include the following. Theovercoating process can be carried out in the absence of any ligand withan aliphatic group. In other words, the procedure can be performedwithout trioctylphosphine oxide (TOPO) or trioctylphosphine (TOP) andinstead use a non-coordinating solvent (e.g., squalane). In order tomaintain solubility of the semiconductor nanocrystals made in thisprocess, multiple distinct aromatic phosphonic acid species and/ormultiple distinct aromatic amine species may be included in the reactionin order to break-up crystallization or ordered packing of ligandspecies (both intra-semiconductor nanocrystal and inter-semiconductornanocrystal) and allow the semiconductor nanocrystals to be dispersed invarious solvent systems. Alternatively, branched phosphonic acids and/orbranched amines can be used for this purpose.

Example 5 Preparation of Semiconductor Nanocrystals Capable of EmittingRed Light with 3,5-Di-Tert-Butyl-4-Hydroxybenzylphosphonic Acid

Synthesis of CdSe Cores:

1 mmol cadmium acetate was dissolved in 8.96 mmol oftri-n-octylphosphine at 100° C. in a 20 mL vial and then dried anddegassed for one hour. 15.5 mmol of trioctylphosphine oxide and 2 mmolof octadecylphosphonic acid were added to a 3-neck flask and dried anddegassed at 140° C. for one hour. After degassing, the Cd solution wasadded to the oxide/acid flask and the mixture was heated to 270° C.under nitrogen. Once the temperature reached 270° C., 8 mmol oftri-n-butylphosphine was injected into the flask. The temperature wasbrought back to 270° C. where 1.1 mL of 1.5 M TBP-Se was then rapidlyinjected. The reaction mixture was heated at 270° C. for 15-30 minuteswhile aliquots of the solution were removed periodically in order tomonitor the growth of the nanocrystals. Once the first absorption peakof the nanocrystals reached 565-575 nm, the reaction was stopped bycooling the mixture to room temperature. The CdSe cores wereprecipitated out of the growth solution inside a nitrogen atmosphereglovebox by adding a 3:1 mixture of methanol and isopropanol. Theisolated cores were then dissolved in hexane and used to make core-shellmaterials.

Preparation of 3,5-Di-tert-butyl-4-hydroxybenzylphosphonic acid

3,5-Di-tert-butyl-4-hydroxybenzylphosphonic acid was obtained from PCISynthesis, 9 Opportunity Way, Newburyport, Mass. 01950.

The preparation of 3,5-Di-tert-butyl-4-hydroxybenzylphosphonic acidutilized the following synthetic approach:

3,5-Di-tert-butyl-4-hydroxybenzylphosphonic acid can be characterized bythe following:

Melting point: 199-200° C. [Lit: 200° C.; Literature ref: J. D. Spivack,FR1555941 (1969)]

IR: 3614 cm⁻¹, 3593 cm⁻¹ (weak, O—H stretching).

¹H-NMR (CD₃OD): δ 7.10 (d, aromatic, 2H, J_(P-H)=2.6 Hz), 5.01 (s,exchanged HOD), 2.99 (d, —CH₂, 2H, J_(P-H)=21.2 Hz), 1.41 (s, —CH₃,18H).

¹³C-NMR (CD₃OD): δ 152.9 (aromatic), 137.9 (aromatic), 126.2 (aromatic),123.5 (aromatic), 34.41 (d, —CH₂, 35.75, 33.07, J_(P-C)=537.2 Hz), 34.35(—C(CH₃)₃), 29.7 (—C(CH₃)₃).

³¹P-NMR (CD₃OD): δ 26.8

The above-identified synthetic precursors included in the preparation of3,5-Di-tert-butyl-4-hydroxybenzylphosphonic acid can be characterized bythe following:

Diethyl 3,5-di-tert-butyl-4-hydroxybenzylphosphonate

Melting point: 119-120° C. (Lit: 118-119° C.; Literature ref: R. K.Ismagilov, Zhur. Obshchei Khimii, 1991, 61, 387).

IR: 3451 cm⁻¹ (weak, —OH, stretching), 2953 (weak, —CH₃, C—Hstretching).

¹H-NMR (CDCl₃): δ 7.066 (d, Ar—H, 2H, J_(P-H)=2.8 Hz), 5.145 (s, 1H,—OH), 4.06-3.92 (m, —CH₂CH₃, 4H, H—H and long-range P—H couplings),3.057 (d, Ar—CH ₂, 2H, J_(P-H)=21.0 Hz), 1.412 (s, —C(CH ₃)₃, 18H),1.222 (t, —CH₂CH ₃, 6H).

¹³C-NMR (CDCl₃): δ 153.98 (aromatic), 136.22 (aromatic), 126.61(aromatic), 122.07 (aromatic), 62.14 (—OCH₂CH₃, J_(P-C)=24.4 Hz), 33.63(Ar—CH₂, J_(P-C)=552.4 Hz), 34.53 [—C(CH₃)₃], 30.54 [—C(CH₃)₃], 16.66(—CH₂ CH₃, J_(P-C)=24.4 Hz).

³¹P-NMR (CDCl₃): δ 28.43.

3,5-di-tert-butyl-4-hydroxybenzyl bromide

Melting point: 51-54° C. (Lit: 52-54° C.; Literature ref: J. D. McClure,J. Org. Chem., 1962, 27, 2365)

IR: 3616 cm⁻¹ (medium, O—H stretching), 2954 cm⁻¹ (weak, alkyl C—Hstretching).

¹H-NMR (CDCl₃): δ 7.20 (s, Ar—H, 2H), 5.31 (s, —OH), 4.51 (s, —CH₂, 2H),1.44 {s, [—C(CH ₃)₃], 18H}.

¹³C-NMR (CDCl₃): δ 154.3 (aromatic), 136.5 (aromatic), 128.7 (aromatic),126.3 (aromatic), 35.8 [(—C(CH₃)₃], 34.6 (—CH₂), 30.5 [—C(CH₃)₃].

Other synthetic approaches that are known or readily ascertainable byone of ordinary skill in the relevant art can be used to prepare3,5-Di-tert-butyl-4-hydroxybenzylphosphonic acid.

Synthesis of CdSe/CdZnS Core-Shell Nanocrystals:

25.86 mmol of trioctylphosphine oxide and 2.4 mmol of3,5-di-tert-butyl-4-hydroxybenzylphosphonic acid were loaded into afour-neck flask. The mixture was then dried and degassed in the reactionvessel by heating to 120° C. for about an hour. The flask was thencooled to 75° C. and the hexane solution containing isolated CdSe cores(0.1 mmol Cd content) was added to the reaction mixture. The hexane wasremoved under reduced pressure. Dimethyl cadmium, diethyl zinc, andhexamethyldisilathiane were used as the Cd, Zn, and S precursors,respectively. The Cd and Zn were mixed in equimolar ratios while the Swas in two-fold excess relative to the Cd and Zn. The Cd/Zn and Ssamples were each dissolved in 4 mL of trioctylphosphine inside anitrogen atmosphere glove box. Once the precursor solutions wereprepared, the reaction flask was heated to 155° C. under nitrogen. Theprecursor solutions were added dropwise over the course of 2 hours at155° C. using a syringe pump. After the shell growth, the nanocrystalswere transferred to a nitrogen atmosphere glovebox and precipitated outof the growth solution by adding a 3:1 mixture of methanol andisopropanol. The isolated core-shell nanocrystals were then dissolved inchloroform and used to make semiconductor nanocrystal compositematerials.

In Table 2, the 3,5-di-tert-butyl-4-hydroxybenzylphosphonic acid ligandgroup is referred to as BHT.

Preparation of Layer Including Semiconductor Nanocrystals

Films listed in Table 2 below are prepared using samples includingsemiconductor nanocrystals prepared substantially in accordance with thesynthesis described in Example 5. Bulk chloroform is removed from thenanocrystal samples with nitrogen purging. Residual chloroform isremoved from the semiconductor nanocrystals under vacuum at roomtemperature. Care is taken not to overdry or completely remove allsolvent.

37 ml of RD-12, a low viscosity reactive diluent commercially availablefrom Radcure Corp, 9 Audrey Pl, Fairfield, N.J. 07004-3401, UnitedStates, is added to 4.68 gram of semiconductor nanocrystals undervacuum. The vessel is then backfilled with nitrogen and the mixture ismixed using a vortex mixer. After the semiconductor nanocrystals arepre-solubilized in the reactive diluent, 156 ml of DR-150, an UV-curableacrylic formulation commercially available Radcure, is added slowlyunder vacuum. The vessel is then backfilled with nitrogen and themixture is mixed using a vortex mixer.

2.00 gram TiO2 (if indicated) is next added and the mixture is mixedwith an homogenizer.

12.00 gram curing agent Escacure TPO is added, following which themixture is mixed with an homogenizer. The vessel including the mixtureis then wrappered with black tape to shield the fluid from light.

The vessel in then backfilled with nitrogen and sonified for at leastabout 3 hours. Care is taken to avoid temperatures over 40 C while thesample is in the ultrasonic bath.

Samples are coated by Mayer rod on precleaned glass slides and cured ina 5000-EC UV Light Curing Flood Lamp from DYMAX Corporation system withan H-bulb (225 mW/cm²) for 10 seconds.

A sample is removed for evaluation and coated on a glass slide with a 52rod and cured for 10 sec:

Thickness =   72 μm FWHM = 36 nm Lambda em = 633.1 nm % A_(450 nm) =82.6% % EQE = 50.0%

Occasionally, the mixing vial is heated to lower viscosity and aidstirring. After the addition is competed, vacuum is pulled to removeentrained air. The vial is then placed in an ultrasonic bath (VWR) from1 hour to overnight, resulting in a clear, colored solution. Care istaken to avoid temperatures over 40 C while the sample is in theultrasonic bath.

Multiple batches of the semiconductor nanocrystals of the same color aremixed together. Prior to making the acrylic preparation. Samples arecoated by Mayer rod on precleaned glass slides and cured in a 5000-EC UVLight Curing Flood Lamp from DYMAX Corporation system with an H-bulb(225 mW/cm²) for 10 seconds.

Samples including multiple layers for achieving the desired thicknessare cured between layers. Samples including filters on top of (or below)the layers including host material and quantum confined semiconductornanoparticles have the filters coated by Mayer rod in a separate step.

Filters are made by blending UV-curable pigment ink formulations fromCoates/Sun Chemical. (Examples include, but are not limited to, DXT-1935and WIN99.) A filter composition is formulated by adding the weightedabsorbances of the individual colors together to achieve the desiredtransmission characteristics.

TABLE 2 Film Color/Sample # Film (Nanocrystal Emission EQE Prep. Example#) Solvent Ligand(s) (nm) FWHM (%) Red/Sample #1 Chloroform BHT 631 3629.0 (without TiO2) (Ex. 5) Red/Sample #2 Chloroform BHT 633 36 50.0(with TiO2) (Ex. 5)Film Characterization:

The films are characterized in the following ways:

-   -   Thickness: measured by a micrometer    -   Emission measurement measured on sample 1 of each type, on Cary        Eclipse. Excitation at 450 nm, 2.5 nm excitation slit, 5 nm        emission slit.    -   Absorption measured at 450 nm on sample 1 of each type, on        Cary 5000. Baseline corrected to blank glass slide.    -   CIE coordinates measured on sample 1 of each type using CS-200        Chroma Meter. Sample excited with 450 nm LED, and camera        collected color data off axis.    -   The external photoluminescent (PL) quantum efficiency is        measured using the method developed by Mello et al. (1). The        method uses a collimated 450 nm LED source, an integrating        sphere and a spectrometer. Three measurements are taken. First,        the LED directly illuminates the integrating sphere giving the        spectrum labeled L1 in FIG. 8. Next, the PL sample is placed        into the integrating sphere so that only diffuse LED light        illuminates the sample giving the (L2+P2) spectrum depicted in        FIG. 8. Finally, the PL sample is placed into the integrating        sphere so that the LED directly illuminates the sample (just off        normal incidence) giving the (L3+P3) spectrum depicted in        FIG. 8. After collecting the data, each spectral contribution        (L's and P's) is computed. L1, L2 and L3 correspond to the sums        of the LED spectra for each measurement and P2 and P3 are the        sums associated with the PL spectra for 2nd and 3rd        measurements. The following equation then gives the external PL        quantum efficiency:        EQE=[(P3·L2) minus (P2·L3)]/(L1·(L2 minus L3))

For additional information concerning EQE measurements, see Mello etal., Advanced Materials 9(3):230 (1997), which is hereby incorporated byreference.

In certain embodiments, semiconductor nanocrystals are purified beforedeposition.

In certain embodiments, a desired ligand can be attached to asemiconductor nanocrystal by building the desired functionality into thephosphonic acid derivative, amine derivative, or both. Following is anon-limiting example of a schematic of a general synthetic procedure forgenerating a desired phosphonic acid derivative:

Also refer to The Chemistry of Organophosphorus Compounds. Volume 4:Ter- and Quinque-Valent Phosphorus Acids and Their Derivatives, Frank R.Hartley (Editor), April 1996 for more general synthetic procedures forgenerating phosphonic acid derivatives.

In certain additional embodiments, a desired ligand can be attached to asemiconductor nanocrystal by building the desired functionality into thephosphonic acid derivative, amine derivative, or both. Following is anon-limiting example of a schematic of a general synthetic procedure forgenerating a desired amine derivative:

Example 6 Comparison of Semiconductor Nanocrystals Prepared With NativeLigands & Semiconductor Nanocrystals with Cap Exchanged Ligands Example6A Preparation of Semiconductor Nanocrystals Capable of Emitting RedLight Including Native Ligands

Synthesis of CdSe Cores:

1 mmol cadmium acetate was dissolved in 8.96 mmol oftri-n-octylphosphine at 100° C. in a 20 mL vial and then dried anddegassed for one hour. 15.5 mmol of trioctylphosphine oxide and 2 mmolof octadecylphosphonic acid were added to a 3-neck flask and dried anddegassed at 140° C. for one hour. After degassing, the Cd solution wasadded to the oxide/acid flask and the mixture was heated to 270° C.under nitrogen. Once the temperature reached 270° C., 8 mmol oftri-n-butylphosphine was injected into the flask. The temperature wasbrought back to 270° C. where 1.1 mL of 1.5 M TBP-Se was then rapidlyinjected. The reaction mixture was heated at 270° C. for 15-30 minuteswhile aliquots of the solution were removed periodically in order tomonitor the growth of the nanocrystals. Once the first absorption peakof the nanocrystals reached 565-575 nm, the reaction was stopped bycooling the mixture to room temperature. The CdSe cores wereprecipitated out of the growth solution inside a nitrogen atmosphereglovebox by adding a 3:1 mixture of methanol and isopropanol. Theisolated cores were then dissolved in hexane and used to make core-shellmaterials.

Synthesis of CdSe/CdZnS Core-Shell Nanocrystals:

25.86 mmol of trioctylphosphine oxide and 2.4 mmol ofoctadecylphosphonic acid were loaded into a four-neck flask. The mixturewas then dried and degassed in the reaction vessel by heating to 120° C.for about an hour. The flask was then cooled to 75° C. and the hexanesolution containing isolated CdSe cores (0.1 mmol Cd content) was addedto the reaction mixture. The hexane was removed under reduced pressureand then 2.4 mmol of 6-amino-1-hexanol was added to the reactionmixture. Dimethyl cadmium, diethyl zinc, and hexamethyldisilathiane wereused as the Cd, Zn, and S precursors, respectively. The Cd and Zn weremixed in equimolar ratios while the S was in two-fold excess relative tothe Cd and Zn. The Cd/Zn and S samples were each dissolved in 4 mL oftrioctylphosphine inside a nitrogen atmosphere glove box. Once theprecursor solutions were prepared, the reaction flask was heated to 155°C. under nitrogen. The precursor solutions were added dropwise over thecourse of 2 hours at 155° C. using a syringe pump. After the shellgrowth, the nanocrystals were transferred to a nitrogen atmosphereglovebox and precipitated out of the growth solution by adding a 3:1mixture of methanol and isopropanol. The isolated core-shellnanocrystals were then dissolved in hexane and their solution-statequantum yield assessed. (QY˜80%)

Example 6B Preparation of Cap Exchanged Semiconductor NanocrystalsCapable of Emitting Red Light

Synthesis of CdSe Cores:

1 mmol cadmium acetate was dissolved in 8.96 mmol oftri-n-octylphosphine at 100° C. in a 20 mL vial and then dried anddegassed for one hour. 15.5 mmol of trioctylphosphine oxide and 2 mmolof octadecylphosphonic acid were added to a 3-neck flask and dried anddegassed at 140° C. for one hour. After degassing, the Cd solution wasadded to the oxide/acid flask and the mixture was heated to 270° C.under nitrogen. Once the temperature reached 270° C., 8 mmol oftri-n-butylphosphine was injected into the flask. The temperature wasbrought back to 270° C. where 1.1 mL of 1.5 M TBP-Se was then rapidlyinjected. The reaction mixture was heated at 270° C. for 15-30 minuteswhile aliquots of the solution were removed periodically in order tomonitor the growth of the nanocrystals. Once the first absorption peakof the nanocrystals reached 565-575 nm, the reaction was stopped bycooling the mixture to room temperature. The CdSe cores wereprecipitated out of the growth solution inside a nitrogen atmosphereglovebox by adding a 3:1 mixture of methanol and isopropanol. Theisolated cores were then dissolved in hexane and used to make core-shellmaterials.

Synthesis of CdSe/CdZnS Core-Shell Nanocrystals:

25.86 mmol of trioctylphosphine oxide and 2.4 mmol ofoctadecylphosphonic acid were loaded into a four-neck flask. The mixturewas then dried and degassed in the reaction vessel by heating to 120° C.for about an hour. The flask was then cooled to 75° C. and the hexanesolution containing isolated CdSe cores (0.1 mmol Cd content) was addedto the reaction mixture. The hexane was removed under reduced pressureand then 2.4 mmol of decylamine was added to the reaction mixture.Dimethyl cadmium, diethyl zinc, and hexamethyldisilathiane were used asthe Cd, Zn, and S precursors, respectively. The Cd and Zn were mixed inequimolar ratios while the S was in two-fold excess relative to the Cdand Zn. The Cd/Zn and S samples were each dissolved in 4 mL oftrioctylphosphine inside a nitrogen atmosphere glove box. Once theprecursor solutions were prepared, the reaction flask was heated to 155°C. under nitrogen. The precursor solutions were added dropwise over thecourse of 2 hours at 155° C. using a syringe pump. After the shellgrowth, the nanocrystals were transferred to a nitrogen atmosphereglovebox and precipitated out of the growth solution by adding a 3:1mixture of methanol and isopropanol. The isolated core-shellnanocrystals were then dissolved in hexane and used for cap exchangereactions. (QY˜80%)

Cap-Exchange Reaction (1) on CdSe/CdZnS Core-Shell Nanocrystals:

10 mL of toluene and 42.6 mmol of 6-amino-1-hexanol were loaded into afour-neck flask. The flask was evacuated and refilled with nitrogenthree times. The flask was then heated to 40° C. and the hexane solutioncontaining isolated CdSe/CdZnS core/shell (1 prep) was added to thereaction mixture. The mixture was heated at 40° C. overnight. Finally,the cap-exchanged semiconductor nanocrystals were precipitated out ofthe growth solution by adding hexane. The isolated core-shellnanocrystals were then dissolved in a 3:1 methanol and isopropanolmixture and their solution-state quantum yield assessed. (QY˜15%)

Cap-Exchange Reaction (2) on CdSe/CdZnS Core-Shell Nanocrystals:

25.86 mmol of trioctylphosphine oxide, 2.4 mmol of octadecylphosphonicacid, and 2.4 mmol of 6-amino-1-hexanol were loaded into a four-neckflask. The mixture was then dried and degassed in the reaction vessel byheating to 120° C. for about an hour. The flask was then cooled to 40°C. and the hexane solution containing isolated CdSe/CdZnS core/shell (1prep) was added to the reaction mixture. The mixture was heated at 40°C. overnight. Finally, the cap-exchanged semiconductor nanocrystals wereprecipitated out of the growth solution by adding a 3:1 mixture ofmethanol and isopropanol. The isolated core-shell nanocrystals were thendissolved in hexane and their solution-state quantum yield assessed.(QY˜19%)

Nanoparticles can have various shapes, including, but not limited to,sphere, rod, disk, other shapes, and mixtures of various shapedparticles.

Metallic nanoparticles can be prepared as described, for example, inU.S. Pat. No. 6,054,495, which is incorporated by reference in itsentirety. The metallic nanoparticle can be a noble metal nanoparticle,such as a gold nanoparticle. Gold nanoparticles can be prepared asdescribed in U.S. Pat. No. 6,506,564, which is incorporated by referencein its entirety. Ceramic nanoparticles can be prepared as described, forexample, in U.S. Pat. No. 6,139,585, which is incorporated by referencein its entirety.

Narrow size distribution, high quality semiconductor nanocrystals withhigh fluorescence efficiency can be prepared using previouslyestablished literature procedures and used as the building blocks. See,C. B. Murray et al., J. Amer. Chem. Soc. 1993, 115, 8706, B. O. Dabbousiet al., J. Phys. Chem. B 1997, 101, 9463, each of which is incorporatedby reference in its entirety. Other methods known or readilyascertainable by the skilled artisan can also be used.

In certain embodiments, nanoparticles comprise chemically synthesizedcolloidal nanoparticles (nanoparticles), such as semiconductornanocrystals or quantum dots. In certain preferred embodiments, thenanoparticles (e.g., semiconductor nanocrystals) have a diameter in arange from about 1 to about 10 nm. In certain embodiments, at least aportion of the nanoparticles, and preferably all of the nanoparticles,include one or more ligands attached to a surface of a nanoparticle.See, C. B. Murray et al., Annu. Rev. Mat. Sci., 30, 545-610 (2000),which is incorporated in its entirety. These zero-dimensional structuresshow strong quantum confinement effects that can be harnessed indesigning bottom-up chemical approaches to create complexheterostructures with electronic and optical properties that are tunablewith the size of the nanocrystals.

Emission from semiconductor nanocrystals can occur at an emissionwavelength when one or more of the nanocrystals is excited. The emissionhas a frequency that corresponds to the band gap of the quantum confinedsemiconductor material. The band gap is a function of the size of thenanocrystal. Nanocrystals having small diameters can have propertiesintermediate between molecular and bulk forms of matter. For example,nanocrystals based on semiconductor materials having small diameters canexhibit quantum confinement of both the electron and hole in all threedimensions, which leads to an increase in the effective band gap of thematerial with decreasing crystallite size. Consequently, both theoptical absorption and emission of nanocrystals shift to the blue (i.e.,to higher energies) as the size of the crystallites decreases.

The emission from a nanocrystal can be a narrow Gaussian emission bandthat can be tuned through the complete wavelength range of theultraviolet, visible, or infrared regions of the spectrum by varying thesize of the nanocrystal, the composition of the nanocrystal, or both.The narrow size distribution of a population of nanocrystals can resultin emission of light in a narrow spectral range. The population can bemonodisperse and can exhibit less than a 15% rms deviation in diameterof the nanocrystals, preferably less than 10%, more preferably less than5%. Spectral emissions in a narrow range of no greater than about 75 nm,preferably 60 nm, more preferably 40 nm, and most preferably 30 nm fullwidth at half max (FWHM) can be observed. The breadth of the emissiondecreases as the dispersity of nanocrystal diameters decreases.

Semiconductor nanocrystals can have high emission quantum efficienciessuch as greater than 10%, 20%, 30%, 40%, 50%, 60%, 70%, or 80%. Thesemiconductor forming the nanocrystals can include Group IV elements,Group II-VI compounds, Group II-V compounds, Group III-VI compounds,Group III-V compounds, Group IV-VI compounds, Group I-III-VI compounds,Group II-IV-VI compounds, or Group II-IV-V compounds, for example, ZnS,ZnSe, ZnTe, CdS, CdSe, CdTe, HgS, HgSe, HgTe, AlN, AlP, AlAs, AlSb, GaN,GaP, GaAs, GaSb, GaSe, InN, InP, InAs, InSb, TlN, TIP, TIAs, TISb, PbS,PbSe, PbTe, or mixtures thereof.

Examples of methods of preparing monodisperse semiconductor nanocrystalsinclude pyrolysis of organometallic reagents, such as dimethyl cadmium,injected into a hot, coordinating solvent. This permits discretenucleation and results in the controlled growth of macroscopicquantities of nanocrystals. Preparation and manipulation of nanocrystalsare described, for example, in U.S. Pat. No. 6,322,901, which isincorporated herein by reference in its entirety. Such methods ofmanufacturing nanocrystals involve a colloidal growth process. Colloidalgrowth occurs by rapidly injecting an M donor and an X donor into a hotcoordinating solvent. The injection produces a nucleus that can be grownin a controlled manner to form a nanocrystal. The reaction mixture canbe gently heated to grow and anneal the nanocrystal. Both the averagesize and the size distribution of the nanocrystals in a sample aredependent on the growth temperature. The growth temperature necessary tomaintain steady growth increases with increasing average crystal size.The nanocrystal is a member of a population of nanocrystals. As a resultof the discrete nucleation and controlled growth, the population ofnanocrystals obtained has a narrow, monodisperse distribution ofdiameters. The monodisperse distribution of diameters can also bereferred to as a size. The process of controlled growth and annealing ofthe nanocrystals in the coordinating solvent that follows nucleation canalso result in uniform surface derivatization and regular corestructures. As the size distribution sharpens, the temperature can beraised to maintain steady growth. By adding more M donor or X donor, thegrowth period can be shortened.

The M donor can be an inorganic compound, an organometallic compound, orelemental metal. For example, M can be cadmium, zinc, magnesium,mercury, aluminum, gallium, indium or thallium. The X donor is acompound capable of reacting with the M donor to form a material withthe general formula MX. Typically, the X donor is a chalcogenide donoror a pnictide donor, such as a phosphine chalcogenide, a bis(silyl)chalcogenide, dioxygen, an ammonium salt, or a tris(silyl) pnictide.Suitable X donors include dioxygen, bis(trimethylsilyl) selenide((TMS)₂Se), trialkyl phosphine selenides such as (tri-n-octylphosphine)selenide (TOPSe) or (tri-n-butylphosphine) selenide (TBPSe), trialkylphosphine tellurides such as (tri-n-octylphosphine) telluride (TOPTe) orhexapropylphosphorustriamide telluride (HPPTTe),bis(trimethylsilyl)telluride ((TMS)₂Te), bis(trimethylsilyl)sulfide((TMS)₂S), a trialkyl phosphine sulfide such as (tri-n-octylphosphine)sulfide (TOPS), an ammonium salt such as an ammonium halide (e.g.,NH₄Cl), tris(trimethylsilyl)phosphide ((TMS)₃P), tris(trimethylsilyl)arsenide ((TMS)₃As), or tris(trimethylsilyl) antimonide ((TMS)₃Sb). Incertain embodiments, the M donor and the X donor can be moieties withinthe same molecule.

A coordinating solvent can help control the growth of nanocrystals. Thecoordinating solvent is a compound having a donor lone pair that, forexample, has a lone electron pair available to coordinate to a surfaceof the growing nanocrystal. Solvent coordination can stabilize thegrowing nanocrystal. Typical coordinating solvents include alkylphosphines, alkyl phosphine oxides, alkyl phosphonic acids, or alkylphosphinic acids, however, other coordinating solvents, such aspyridines, furans, and amines may also be suitable for the nanocrystalproduction. Examples of suitable coordinating solvents include pyridine,tri-n-octyl phosphine (TOP), tri-n-octyl phosphine oxide (TOPO) andtris-hydroxylpropylphosphine (tHPP). Technical grade TOPO can be used.

In certain methods, a non-coordinating or weakly coordinating solventcan be used.

Size distribution during the growth stage of the reaction can beestimated by monitoring the absorption line widths of the particles.Modification of the reaction temperature in response to changes in theabsorption spectrum of the particles allows the maintenance of a sharpparticle size distribution during growth. Reactants can be added to thenucleation solution during crystal growth to grow larger crystals. Bystopping growth at a particular nanocrystal average diameter andchoosing the proper composition of the semiconducting material, theemission spectra of the nanocrystals can be tuned continuously over thewavelength range of 300 nm to 5 microns.

Semiconductor nanocrystals include, for example, inorganic crystallitesbetween about 1 nm and about 1000 nm in diameter, preferably betweenabout 2 nm and about 50 um, more preferably about 1 nm to about 20 nm(such as about 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20nm).

A semiconductor nanocrystal typically has a diameter of less than 150 Å.A population of nanocrystals preferably has average diameters in therange of 15 Å to 125 Å.

The nanocrystal can be a member of a population of nanocrystals having anarrow size distribution. The nanocrystal can be a sphere, rod, disk, orother shape. The nanocrystal can include a core of a semiconductormaterial. The nanocrystal can include a core having the formula MX,where M comprises one or more metals (e.g., but not limited to, cadmium,zinc, magnesium, mercury, aluminum, gallium, indium, thallium, ormixtures thereof), and X comprises one or more members of Group IV, V,or VI (e.g., but not limited to, oxygen, sulfur, selenium, tellurium,nitrogen, phosphorus, arsenic, antimony, or mixtures thereof). Incertain embodiments, a nanocrystal can comprise a Group II-VI compound,Group II-V compound, Group III-VI compound, Group III-V compound, GroupIV-VI compound, Group I-III-VI compound, Group II-IV-VI compound, andGroup II-IV-V compound. In certain embodiments, a nanocrystal cancomprise a Group IV element.

The core can have an overcoating on a surface of the core. Theovercoating can be a semiconductor material having a compositiondifferent from the composition of the core. The overcoat of asemiconductor material on a surface of the nanocrystal can include aGroup II-VI compound, Group II-V compound, Group III-VI compound, GroupIII-V compound, Group IV-VI compound, Group I-III-VI compound, GroupII-IV-VI compound, and Group II-IV-V compound, for example, ZnS, ZnSe,ZnTe, CdS, CdSe, CdTe, HgS, HgSe, HgTe, AlN, AlP, AlAs, AlSb, GaN, GaP,GaAs, GaSb, GaSe, InN, InP, InAs, InSb, TlN, TIP, TIAs, TISb, PbS, PbSe,PbTe, or mixtures thereof. In certain embodiments, a nanocrystal cancomprise a Group IV element.

For example, ZnS, ZnSe or CdS overcoatings can be grown on CdSe or CdTenanocrystals. An overcoating process is described, for example, in U.S.Pat. No. 6,322,901. By adjusting the temperature of the reaction mixtureduring overcoating and monitoring the absorption spectrum of the core,over coated materials having high emission quantum efficiencies andnarrow size distributions can be obtained.

The particle size distribution can be further refined by size selectiveprecipitation with a poor solvent for the nanocrystals, such asmethanol/butanol as described in U.S. Pat. No. 6,322,901. For example,nanocrystals can be dispersed in a solution of 10% butanol in hexane.Methanol can be added dropwise to this stirring solution untilopalescence persists. Separation of supernatant and flocculate bycentrifugation produces a precipitate enriched with the largestcrystallites in the sample. This procedure can be repeated until nofurther sharpening of the optical absorption spectrum is noted.Size-selective precipitation can be carried out in a variety ofsolvent/nonsolvent pairs, including pyridine/hexane andchloroform/methanol. The size-selected nanocrystal population can haveno more than a 15% rms deviation from mean diameter, preferably 10% rmsdeviation or less, and more preferably 5% rms deviation or less.

Transmission electron microscopy (TEM) can provide information about thesize, shape, and distribution of the nanocrystal population. Powderx-ray diffraction (XRD) patterns can provided the most completeinformation regarding the type and quality of the crystal structure ofthe nanocrystals. Estimates of size are also possible since particlediameter is inversely related, via the X-ray coherence length, to thepeak width. For example, the diameter of the nanocrystal can be measureddirectly by transmission electron microscopy or estimated from x-raydiffraction data using, for example, the Scherrer equation. It also canbe estimated from the UV/Vis absorption spectrum.

Narrow FWHM of nanocrystals can result in saturated color emission. Thiscan lead to efficient nanocrystal-light emitting devices even in the redand blue parts of the spectrum, since in nanocrystal emitting devices nophotons are lost to infrared and UV emission. The broadly tunable,saturated color emission over the entire visible spectrum of a singlematerial system is unmatched by any class of organic chromophores.Furthermore, environmental stability of covalently bonded inorganicnanocrystals suggests that device lifetimes of hybrid organic/inorganiclight emitting devices should match or exceed that of all-organic lightemitting devices, when nanocrystals are used as luminescent centers. Thedegeneracy of the band edge energy levels of nanocrystals facilitatescapture and radiative recombination of all possible excitons, whethergenerated by direct charge injection or energy transfer. The maximumtheoretical nanocrystal-light emitting device efficiencies are thereforecomparable to the unity efficiency of phosphorescent organic lightemitting devices. The nanocrystal's excited state lifetime (τ) is muchshorter (τ˜10 ns) than a typical phosphor (τ>0.5 μs), enablingnanocrystal-light emitting devices to operate efficiently even at highcurrent density.

Semiconductor nanocrystals in accordance with the present inventions canbe included in emissive materials for use in light-emitting devices,displays, and other optoelectronic and electronic devices, including,but not limited to, those described, for example, in InternationalApplication No. PCT/US2007/013152, entitled “Light-Emitting Devices AndDisplays With Improved Performance”, of QD Vision, Inc. et al., filed 4Jun. 2007, which is hereby incorporated herein by reference in itsentirety.

Semiconductor nanocrystals in accordance with the present inventions canbe included in photoluminescent applications including, but not limitedto, those described in U.S. Application No. 60/971,885, of Coe-Sullivan,et al., entitled “Optical Component, System Including An OpticalComponent, Devices, And Composition”, filed 12 Sep. 2007, and U.S.Application No. 60/973,644, entitled “Optical Component, SystemIncluding An Optical Component, Devices, And Composition”, ofCoe-Sullivan, et al., filed 19 Sep. 2007, each of which is herebyincorporated herein by reference in its entirety.

Other materials, techniques, methods, applications, and information thatmay be useful with the present invention are described in InternationalPatent Application No. PCT/US2007/24750, entitled “Improved CompositesAnd Devices Including Nanoparticles”, of Coe-Sullivan, et al, filed 3Dec. 2007, and U.S. Application No. 60/971,887, entitled “FunctionalizedSemiconductor Nanocrystals And Method”, of Breen, et al., filed 12 Sep.2007; and International Application No. PCT/US2007/014711, entitled“Methods For Depositing Nanomaterial, Methods For Fabricating A Device,And Methods For Fabricating An Array Of Devices”, of QD Vision, Inc. etal., filed 25 Jun. 2007; each of the foregoing being hereby incorporatedherein by reference in its entirety.

As used herein, the singular forms “a”, “an” and “the” include pluralunless the context clearly dictates otherwise. Thus, for example,reference to an emissive material includes reference to one or more ofsuch materials.

When an amount, concentration, or other value or parameter is given aseither a range, preferred range, or a list of upper preferable valuesand lower preferable values, this is to be understood as specificallydisclosing all ranges formed from any pair of any upper range limit orpreferred value and any lower range limit or preferred value, regardlessof whether ranges are separately disclosed. Where a range of numericalvalues is recited herein, unless otherwise stated, the range is intendedto include the endpoints thereof, and all integers and fractions withinthe range. It is not intended that the scope of the invention be limitedto the specific values recited when defining a range.

The terms and expressions which have been employed herein are used asterms of description and not of limitation, and there is no intention inthe use of such terms and expressions of excluding equivalents of thefeatures shown and described, or portions thereof, it being recognizedthat various modifications are possible within the scope of theinvention claimed. Moreover, any one or more features of any embodimentof the invention may be combined with any one or more other features ofany other embodiment of the invention, without departing from the scopeof the invention. Additional embodiments of the present invention willalso be apparent to those skilled in the art from consideration of thespecification and practice of the invention disclosed herein. It isintended that the specification and examples be considered as exemplaryonly, with a true scope and spirit of the invention being indicated bythe following claims and equivalents thereof.

All patents, patent applications, and publications mentioned above areherein incorporated by reference in their entirety for all purposes.None of the patents, patent applications, and publications mentionedherein are admitted to be prior art.

What is claimed is:
 1. A nanoparticle including one or more chemicallydistinct native ligands attached to a surface thereof, at least one ofsaid ligands being represented by the formula:X-Sp-Z wherein X represents a secondary amine group; Sp represents aspacer group, such as a group capable of allowing a transfer of chargeor an insulating group; and Z represents: (i) a reactive group capableof communicating specific chemical properties to the nanoparticle aswell as provide specific chemical reactivity to the surface of thenanoparticle, and/or (ii) a group that is cyclic, halogenated, and/orpolar a-protic, wherein Z in all cases is not reactive upon exposure tolight, and wherein a native ligand is a ligand that attaches orcoordinates to the nanoparticle surface during the growth thereof orovercoating thereof with an overcoating material comprising asemiconductor material.
 2. A nanoparticle in accordance with claim 1wherein Z does not render the nanoparticle dispersible in a liquidmedium that includes water.
 3. A nanoparticle in accordance with claim 1wherein the reactive group comprises a functional, bifunctional, orpolyfunctional reagent, and/or a reactive chemical group.
 4. Ananoparticle in accordance with claim 1 wherein the cyclic groupcomprises a saturated or unsaturated cyclic or bicyclic compound oraromatic compound.
 5. A nanoparticle in accordance with claim 1 whereinthe cyclic group includes at least one hetero-atom and/or at least onesubstituent group.
 6. A nanoparticle in accordance with claim 1 whereinthe halogenated group comprises a fluorinated group, perfluorinatedgroup, a chlorinated group, a perchlorinated group, a brominated group,a perbrominated group, an iodinated group, a periodinated group.
 7. Ananoparticle in accordance with claim 1 wherein the polar a-protic groupcomprises a ketone, aldehyde, amide, urea, urethane, or an imine.
 8. Ananoparticle in accordance with claim 1 wherein the nanoparticlecomprises a semiconductor material.
 9. A nanoparticle in accordance withclaim 1 wherein the nanoparticle comprises a semiconductor nanocrystal.10. A nanoparticle in accordance with claim 1 wherein the nanoparticlecomprises a core comprising a first material and a shell disposed overat least a portion of a surface of the core, the shell comprising asecond material.
 11. A nanoparticle in accordance with claim 10 whereinthe first material comprises a semiconductor material.
 12. Ananoparticle in accordance with claim 10 wherein the second materialcomprises a semiconductor material.
 13. A nanoparticle in accordancewith claim 10 wherein one or more additional shells are disposed over atleast a portion of a surface of the shell.
 14. A nanoparticle inaccordance with claim 9 wherein the semiconductor nanocrystal comprisesa core comprising a first material and a shell disposed over at least aportion of a surface of the core, the shell comprising a secondmaterial.
 15. A nanoparticle in accordance with claim 1 wherein theligand represented by the formula X-Sp-Z comprises an organic amineincluding a terminal hydroxyl group or a fluorinated organic amine. 16.A nanoparticle in accordance with claim 1 wherein the nanoparticleincludes two or more chemically distinct native ligands attached to asurface thereof, at least one of said ligands being represented by theformula:X-Sp-Z.
 17. A nanoparticle in accordance with claim 1 wherein thenanoparticle has higher quantum yield than if the same ligand wasattached to the nanoparticle by a ligand exchange process.
 18. Ananoparticle in accordance with claim 9 wherein the nanoparticleincludes two or more chemically distinct native ligands attached to asurface thereof, at least one of said ligands being represented by theformula:X-Sp-Z.
 19. A nanoparticle in accordance with claim 9 wherein the ligandrepresented by the formula X-Sp-Z comprises an organic amine including aterminal hydroxyl group or a fluorinated organic amine.
 20. Ananoparticle in accordance with claim 1 wherein Sp comprises a straightor branched C₁-C₁₈ hydrocarbon chain.